ISli 


Moorish  salon  in  the  Continental  Hotel  lighted  by  the  Jablochkoff  candle. 


THE 


ELECTEIC   LIGHT 

ITS  HISTORY,  PRODUCTION,  AND 
APPLICATIONS. 


BY 

EM.  ALGLAVE  AND  J.  BOULAKD. 

TRANSLATED  FROM  THE  FRENCH  BY 

T.   O'CONOR    SLOANE,  E.  M.,  PH. I), 

EDITED,  WITH   NOTES   AND   ADDITIONS,  BY 

C.    M.    LUISTGREN,    C.  E. 


ILLUSTRATED  WITH  TWO  HUNDRED  AND  FIFTY-TWO  WOODCUTS. 


NEW  YORK: 
D.    APPLETON   AND    COMPANY, 

1,  3,  AND  5  BOND  STEEET. 

1884. 


COPYRIGHT,  1884, 
BY   D.   APPLETON    AND    COMPANY. 


EDITOE'S    PEEFAOE. 


THOUGH  there  are  already  a  number  of  popular  exposi- 
tions of  the  subject  of  electric  lighting,  the  work  of  Messrs. 
Alglave  and  Boulard  has  been  thought  to  have  sufficiently 
distinctive  merits  to  warrant  its  introduction  to  the  English- 
reading  public. 

While  not  pretending  to  be  an  exhaustive  presentation  of 
the  subject,  the  exposition  will  be  found  to  be  sufficiently  full 
to  enable  the  reader  to  understand  the  essential  features  of 
present  electric-lighting  apparatus,  and  to  appreciate  the 
character  of  the  problems  which  had  to  be  solved  before 
this  method  of  illumination  could  enter  upon  an  industrial 
career. 

In  adding  to  the  work  of  the  authors  I  have  made  no  at- 
tempt to  introduce  either  all  of  the  lamps  and  machines 
which  have  been  devised,  or  even  all  of  those  which  have 
passed  into  actual  use.  The  additions  of  this  kind  which 
have  been  made  are  either  later  forms  of  the  apparatus  de- 
scribed by  the  authors,  or  those  which  have  distinctive  feat- 
ures of  interest  of  their  own.  The  chief  additions  which 
I  have  thought  it  desirable  to  make  relate  to  the  general 
aspects  of  the  subject,  rather  than  to  special  forms  of  ap- 
paratus. Changes  have  been  found  necessary  throughout 
the  text,  either  in  correction  of  erroneous  statements,  or  in 
amplification  of  insufficient  ones,  but  these  are  in  all  cases 
inclosed  in  brackets,  as  are  the  additional  chapters  and  sec- 
tions, and  the  notes. 


iv  EDITOK'S  PREFACE. 

I  have  to  express  my  indebtedness  to  Mr.  Edison,  the 
United  States  Electric  Lighting,  Fuller  Electrical,  and  Brush 
Electric  Companies,  for  information  concerning  their  various 
systems,  and  cuts  illustrating  their  apparatus. 

C.  M.  L. 

NEW  YORK,  April,  1884. 


PEE  FA  0  E. 


years  ago,  it  was  generally  admitted  that  the  role  of 
electricity  was  practically  confined  to  telegraphy  and  electro- 
plating. Outside  of  these  two  uses  it  seemed  destined  to  re- 
main a  costly  curiosity,  available  at  the  best  in  those  cases 
in  which  ordinary  economy  could  be  left  out  of  account,  in 
the  presence  of  necessities  not  governed  by  expense,  as  in 
theatres  and  light-houses.  But,  since  the  invention  of  the 
Gramme  machine,  the  rapidity  of  its  daily  progress  has  as- 
tonished the  most  sanguine.  The  International  Exhibition  at 
Paris  was  a  genuine  revelation  to  the  public,  and  perhaps 
even  to  many  savants.  In  spite  of  its  scientific  character,  its 
success  exceeded  all  expectations,  and  its  popularity  proved 
that  the  public  began  to  understand  the  important  role  that 
electricity  already  fills  in  the  life  of  society,  and  to  divine  the 
still  greater  importance  reserved  for  it  in  the  near  future. 

This  exhibition,  which  may  justly  be  termed  educating, 
was  principally  instituted  and  advocated  by  the  founders  of 
a  journal  of  electricity,  bearing  the  same  name  as  this  book, 
"  La  Lumiere  filectrique." 

The  original  committee  comprised  among  others  Dr.  Cor- 
nelius Herz ;  M.  Adrien  Hebard,  senator,  and  editor  of  the 
" Temps"  ;  M.  Jules  Bapst,  editor  of  the  "Debats" ;  M.  Jaques 
de  Reinach  ;  and  M.  Georges  Berger,  who  was  Commissioner- 
General  of  the  Exhibition.  The  project,  warmly  supported 
from  the  beginning  by  the  Minister  of  Public  Works,  M. 
Yarroy,  finally  reached  its  consummation  under  the  patron- 
age of  the  Minister  of  Mails  and  Telegraphs,  M.  Cochery, 


vi  PREFACE. 

and  supported  by  the  successor  of  M.  Varroy  in  the  Ministry 
of  Public  Works,  M.  Sadi  Carnot. 

The  success  of  a  large  fortnightly  journal,  devoted  exclu- 
sively to  electricity,  is  another  proof  of  the  growing  impor- 
tance of  this  branch  of  physical  science,  which  promises  to  be 
more  fertile  than  all  the  others  in  industrial  applications. 
Further,  we  must  state  that  there  exist  in  Paris  alone  one  or 
two  other  periodicals  also  devoted  to  electricity  and  its  appli- 
cations. 

This  book  is  devoted  entirely  to  that  one  of  the  applications 
of  electricity,  which,  without  doubt,  is  about  to  experience  the 
most  rapid  practical  development :  we  refer  to  artificial  light- 
ing. But,  for  the  economist  as  well  as  for  the  engineer,  the 
use  of  the  electric  light  belongs  to  the  general  applications  of 
electricity,  on  account  of  the  question  of  the  distribution  of 
this  physical  agent,  which  now  can  be  utilized  by  the  general 
public.  We  shall  never  have  cheap  electricity  until  the  day 
comes  when  it  shall  be  distributed  to  each  individual  house  by 
such  a  system  as  that  used  for  gas,  and  then  it  will  distribute 
power  as  well  as  light.  This  marvelous  result  is  not  only 
possible  but  easy  of  accomplishment  to-day.  The  important 
labors  of  M.  Marcel  Deprez,  detailed  in  the  fifth  book  of  this 
work,  furnish  a  complete  solution,  founded  upon  discoveries 
which  have  greatly  modified  the  theories  generally  accepted 
up  to  the  present  time.  The  first  experiments  have  brilliant- 
ly confirmed  the  previsions  of  the  inventor,  who  is  now  pre- 
paring to  reproduce  them  on  a  large  scale. 

The  system  of  electrical  distribution  of  M.  Marcel  Deprez 
has  more  than  an  industrial  interest ;  its  importance  is  also 
great  from  a  social  point  of  view,  for  it  may  perhaps  modify 
the  economic  development  of  the  modern  world.  The  con- 
centration of  industrial  processes  in  immense  factories  where 
the  workman  loses  his  individuality  and  his  originality,  has 
hitherto  seemed  an  inevitable  consequence  of  the  domination 
of  mechanical  motors,  because  small  heat-engines  are  too 
costly  to  render  possible  the  distribution  of  work  in  the 
family  workshops.  Electricity,  on  the  other  hand,  does  not 


PREFACE.  vii 

suffer  the  same  losses  in  being  divided  so  as  to  be  put  at  the 
disposition  of  the  humblest.  It  can  penetrate  the  poorest  of 
garrets  by  a  wire  similar  to  a  bell-wire,  and  then  can  drive 
the  smallest  sewing-machine,  at  almost  the  same  .cost,  in  pro- 
portion to  the  power  employed,  as  if  it  were  actuating  the 
largest  class  of  machinery.  The  turning  of  a  switch  suffices  to 
give  immediately,  and  to  the  full  extent,  the  quantity  of  power 
desired,  and  to  make  it  vary  at  will,  without  any  loss  when 
the  work  is  interrupted  or  diminished. 

Doubtless  electricity,  thus  under  perfect  control,  will  not 
be  able  to  re-establish  a  complete  equality  between  the  large 
and  small  producer.  But  the  contest  will  become  possible  in 
many  cases,  and  the  development  of  the  smaller  industries 
will  furnish  the  workman,  desirous  of  raising  himself  to  the 
rank  of  master,  an  ideal  less  inaccessible  for  him  than  is  the 
proprietorship  of  Creusot. 

In  such  a  question  as  this,  the  initiative  should  be  taken 
by  the  Municipal  Council  of  Paris,  because  it  alone  can 
authorize  and  encourage  effectively  the  general  distribution 
of  electricity  in  the  city  where  such  distribution  can  render 
the  greatest  services.  To  take  this  initiative  it  has  only  to 
persevere  in  the  way  it  has  followed  for  the  last  three  years. 
The  Universal  Exhibition  of  1878  showed  us  the  advent  of 
the  electric  light  upon  the  principal  streets  of  the  capital. 
The  Exhibition  of  1881  should  leave  us  as  a  souvenir  a  gen- 
eral distribution  of  power  and  light  by  electricity.  We  may 
hope  that  the  Municipal  Council  of  Paris  will  not  hesitate 
in  a  question  where  the  democratic  spirit  so  happily  allies 
itself  with  the  scientific. 


CONTENTS. 


BOOK  I. 

HISTORY  OF  ARTIFICIAL  LIGHTING. 

CHAPTER  PAGE 

I.   Oils,  candles,  and  gas             .       •    -v  .         •            •  *           •            •        1 

II.   History  of  the  electric  light        .        •---»..          .           .  *           .            11 

BOOK  II. 
THE  VOLTAIC  ARC. 

I.  How  the  electric  light  is  produced    .            .           .  .            .27 

II.   Electrical  units     .            .           '*•    '    " '  .            ..           .  .            .             37 

III.  The  arc-lamp  carbons             .            .            »            .  .            .            .46 

IV.  Single-light  regulators     .......  55 

I.   Regulators  with  electro-magnet      .            .  .            .            .60 

II.   Solenoid  regulators        .          •  . :           ....  67 

V.   Multiple  light,  or  division,  regulators          »    <        .  .            .            .71 

I.   Derived-current,  or  shunt-circuit,  lamps  .            .             72 

II.   Differential  lamps    .                        .            .  .            .            .78 

III.  Automatic  safety  apparatus  r                       90 

VI.   The  Jablochkoff  candle          .         '. 98 

VII.   Lamps  without  mechanism         .            .            .            .  .            .           105 

I.  Lamps  with  converging  carbons     .  .           .            .    105 

II.  Recent  candles  .  110 


BOOK  III. 

THE  INCANDESCENT  LIGHT. 

I.  History  of  incandescence       .            .           .           .  .            .            .116 

I.   The  debut  of  platinum  .            .'           .  .            .            .           116 

II.   The  debut  of  carbon             .            .            .  .            .            .117 

III.   The  Russian  lamps        .            .            .  .'           .            .           119 

II.  Incandescence  in  the  open  air           .            .           .  .           .           .123 

I.   The  Reynier  lamp 123 

II.   The  Werdermann  lamp       .  '          .            .  .            .            .125 


CONTENTS. 

PAGE 

III.  The  actual  Reynier-Werdermann  lamps       .           .           .  128 

IV.  Installation  of  Keynier-Werdermann  lamps        .           .  .    132 
V.  Various  lamps  .......  134 

III.  The  sun  lamp            .           .           .           .           .            .           .  .137 

IV.  The  Edison  lamp           .            .            .           .           .           .           .  148 

I.   His  first  researches  ......     148 

II.   Platinum-wire  lamps  .            .            .            .                        .  152 

III.  Lamps  with  paper  carbon              .            .            .            .  .156 

IV.  Bamboo-carbon  lamps             .....  158 
V.   The  lamps  actually  employed       .            .            .            .  .164 

V.  The  Swan,  Lane-Fox,  Maxim,  and  new  lamps             .           .           .  170 

I.   The  Swan  lamp      .            .            .            <            .            .  .170 

II.   The  Lane-Fox  lamp    .            ....            .  177 

III.  The  Maxim  lamp  .           .           .           .           .           .  .179 

IV.  New  lamps       .            .           .           .           .           .           .  180 

VI.   Measurement  of  incandescent  lamps           .            .            .            .  .182 

VII.  Conditions  of  efficiency  in  the  incandescent  lamp      .           .           .  187 


BOOK  IV. 

PRODUCTION  OF  ELECTRIC  CURRENTS. 

I.  Hydro-electric  batteries       .  .  .  .  .  .  .196 

Secondary  or  storage  batteries  ....  202 

II.   Thermo-electric  batteries     .......  207 

III.  Electrical  induction       .  .  .  .  .  .  .  211 

Ruhmkorff's  coil    .  .  .  .  .  .  .214 

IV.  Theoretical  principles  of  machines       .            .            .    '        .            .  217 
V.   The  first  magneto-electric  machines            .....  232 

I.   Nollet.— Van  Malderen.— Holmes      ....  233 

II.   Siemens.— Wilde.— Ladd 236 

VI.  The  Gramme  machine    .......  240 

Division  machines  (Machines  d  division)  .  .  .  245 

Octagonal  machines     ......  248 

Alternating-current  machines       .....  248 

Self-exciting  machines  .....  250 

Precursors  of  Gramme       ......  255 

VII.   The  Siemens  machines. — Ferranti  and  Gordon  machines       .  .  257 

VIII.   Recent  dynamo-electric  machines    ......  266 

I.  Weston  machine          .  .  .  .  .  .266 

II.   Maxim  machine      .......  267 

III.  Edison  machine  .  .  .  .  .  .273 

IV.  Transformations  of  the  preceding  machines        .            .            .  279 
V.   Machines  in  which  the  cores  of  the  armature  coils  play  a  pre- 
ponderating role     ......  286 

IX.   Recent  magneto-electric  machines  ......  290 

X.   Efficiency  of  the  dynamo  ......  298 

XI.  Measurements  of  dynamos  and  arc-lamps  .....  304 


CONTENTS.  xi 


BOOK  V. 

DISTRIBUTION  OF  ELECTRICITY. 

CHAPTER  PAGE 

I.  First  mode  of  distribution         .           .            .            .            .            .  314 

I.   Electric  conductors           ......  315 

II.  Disposition  of  electric  wires  for  lighting  the  port  of  Havre  317 

II.   Conditions  of  a  general  distribution     .....  324 

I.   Regulators  of  the  intensity  of  currents    ....  326 

II.  Electric  canalization  of  Edison          ....  329 

III.  M.  Gravier's  system  of  electrical  distribution      .            .            .  333 

IV.  System  of  electrical  distribution  of  M.  Marcel  Deprez         .  338 
V.   Edison's  method  of  regulation      .....  345 

VI.  Weston's  method  of  regulation. — Brush  regulator    .            .  350 

III.  Economy  of  conductors        .            .            .            .            f                        .  354 

I.   Edison's  multiple-series  system  of  distribution          4            ...  .  355 

II.   The  secondary-generator  system  of  distribution  .            .            .  357 

IV.  Divisibility  of  the  electric  light             .            .                       .           .  359 
V.  Electric  meters                                                                                             .  363 


BOOK  VI. 

APPLICATIONS  OF  THE  ELECTRIC  LIGHT. 

I.  Electricity  in  light-houses         .  .  .'         .  .  .  371 

II.  The  electric  light  in  war  and  navigation    .....  388 

I.  Military  and  maritime  applications  from  1855  to  1877         .  388 

II.   Electric  projectors  of  the  French  army   ....  394 

III.   The  electric  light  at  sea          .  .  .  .  .  399 

III.  The  electric  light  in  the  theatre  , 407 

IV.  Industrial  applications  .  .  .    .       t  .  .  ,  417 


LIST    OF    ILLUSTEATIOIsrS. 


FIG. 

FRONTISPIECE — Moorish  saloon  of  the  Continental  Hotel,  lighted  by  Ja- 
blochkoff  candles. 

1.  Pincers  for  lamp  .  .  .  .  .  .  .          ' .  .2 

2.  Bronze  Roman  lamp .  ..-  .       «  . 

3.  Hook  for  lamp     .  .  .  .  .  ...  .  .2 

4.  5.  Roman  candelabra  in  carved  bronze,  bearing  one  or  more  lamps         .  3 

6.  Quinquet's  lamp  hung  upon  a  wall         .  .  .  ...      6 

7.  Lamp  of  the  Carcel  type,  with  moderator  mechanism,  and  bottom  oil- 

reservoir  .,  •  f  ...  •  »  •  •"-'         7 

8.  Lamp  of  M.  Tessie  du  Motay  for  production  of  the  Drummond  light  .     10 

9.  Hawksbee  experimenting  with  Otto  von  Guericke's  electric  machine,  in 

England .  .  .  12 

10.  Franklin  making  the  experiment  with  a  kite,  to  establish  the  identity  of 

lightning  and  electricity       .          . .          - »  .  .  .  .14 

11.  Experiment  of  electrifying  a  woman,  from  an  engraving  of  the  eighteenth 

century     .            .            .            .                       .           .           .  .17 

12.  The  Abbe  Nollet  giving  a  lesson  in  electricity  .           .           .  .            .19 

13.  Electrometer,  after  the  design  in  the  Encyclopaedia          ...  20 

14.  The  Avenue  de  1'Opera  in  Paris  lighted  by  Jablochkoff  candles  .            .    26 

15.  The  two  poles  of  the  voltaic  arc       .            .            .....  .           33 

16.  Draw-plate,  with  hydraulic  press,  for  making  artificial  carbons  .            .    48 

17.  Curved  nozzle  draw-press  of  M.  Napoli.    (Vertical  section.)         .  .           50 

18.  Cylinder  for  nourishment  of  the  carbons  under  pressure,  by  M.  Napoli's 

method  .  .  .  .  •  ,-  •  •  •    50 

19.  Workshop  of  M.  Napoli,  showing  the  different  operations  of  manufacturing 

electric-light  carbons      .        "  «,    '        *  •.         '  <•  .  .  52 

20.  21,  22.  Points  of  a  pair  of  carbons,  plain,  and  coated  with  metal        .  .    53 

23.  One-sided  position  of  the  carbons,  for  the  purpose  of  causing  the  light  to  be 

of  greater  intensity  in  one  direction      .       ^^-^ , ...  56 

24.  Carbon-holder  regulated  by  hand,  for  the  production  of^the  electric  light    .  57 

25.  Primitive  carbon-holder,  for  production  of  the  electric  light  in  a  vacuum  57 

26.  Hand-regulator  of  M.  Boudreaux,  with  vertical  carbon-iolders,  for  magic 

lanterns  and  other  experiments  with  electric  light            .          -„  '  .58 

27.  Harrison's  regulator  (1857)   .            .            .            .           1           .            .  59 

28.  First  regulator  of  the  electric  light  of  Foucault  (1849)            ,            .  .62 

29.  Regulator  of  J.  Duboscq       .            .            .                     ^>            •            *  ^ 

30.  Serrin's  regulator  (1859>  .            .           .           .           .      \     .           .  .64 

31.  Burgin's  regulator     .            .           .....         .....  65 


xiv  LIST  OF  ILLUSTRATIONS. 

FIG.  PAGE 

32.  Archereau's  regulator,  type  of  solenoid  regulators      .  .  .  .67 

33.  Gaiffe's  regulator     ........  68 

34.  Jaspar's  regulator          ........      69 

35.  F.  Carre's  regulator  .......  70 

36.  Serrin  regulator  modified  for  derived  current  by  the  Lontin  company        .       73 

37.  M.  Gramme's  derived-current  regulator    .....  75 

38.  De  Mersanne  regulator .  .  .  .  .  .  .76 

39.  Section  of  the  carbon-carrier  of  the  De  Mersanne  regulator       .  .  76 

40.  The  Wallace  lamp 77 

41.  Siemens  differential  lamp  .......  79 

42.  Gerard  lamp       .  .  .  .  .  .  .  .  .81 

43.  Brush  lamp  .........  83 

44.  Vertical  section  of  the  upper  carbon-rod         .  .  .  .  .83 

45.  Relation  of  the  two  carbon-rods  to  each  other  in  the  double  lamp         .  84 

46.  Brush  double  lamp        ........      84 

47.  A  street  of  New  York  lighted  by  Brush  lamps     ....  85 

48.  Brush  street-lamp          .  .  .  .  .  .  .      86 

49.  Weston  lamp  ........  87 

50.  Details  of  the  mechanism  of  the  Weston  lamp  .  .  .  .88 

51.  Section  of  one  of  the  differential  magnets  of  the  Weston  lamp  .  .  88 

52.  Mechanism  of  the  Weston  lamp  .  .  .  .  .  .89 

53.  Vertical  section  of  operating  parts  of  the  Weston  lamp  ...  90 

54.  Clutch  of  the  Weston  lamp 90 

55.  Mechanism  of  the  Wood  lamp        .  .  .  .  .  .  91 

56.  Diagram  of  the  working  parts  of  the  Wood  lamp       .  .  .  .92 

57.  Wood  single  lamp   ........  93 

58.  Gerard  automatic  cut-out          .  .  .  .  .  .  .94 

59.  Safety-box  of  M.  de  Mersanne       ......  95 

60.  Diagram  of  Brush  lamp  connections  and  cut-out       .  .  .  .96 

61.  Weston  automatic  cut-out  .  .  .  .  .  .  .  97 

62.  63,  64.  Jablochkoff  candle 100 

65.  Sockets  of  Jablochkoff  candles  and  switch  for  lighting  the  candles  succes- 

sively by  hand  ........  102 

66.  The  Hippodrome  of  Paris  lighted  by  Jablochkoff  candles     .  .  .     104 

67.  Rapieff  arc-lamp      ........  106 

68.  Gerard  lamp.     General  appearance      .  .  .  .  .  .108 

69.  Vertical  section  of  Gerard  lamp     ......  109 

70.  Wilde's  candle.     Four-candle  holder  .  .  .  .  .  .111 

71.  Jamin  candle  .  .  .  .  .  .  .  .113 

72.  A  street  in  Newcastle  lighted  by  the  Swan  incandescent  lamp         .  .120 

73.  Incandescent  lamp  of  Konn,  in  a  closed  vessel     .  .  .  .  122 

74.  Principle  of  incandescence  ii  the  open  air      .  .  .  .  .124 

75.  Reynier  incandescent  lamp ;  first  arrangement  with  rotating  electrode .  124 

76.  Magnified  image  o'^he  incandescent  portion  of  the  Reynier  lamp  .  .     125 

77.  Werdermann  lamp  ........  126 

78.  Burner  of  the  Reyrier  lamp      .......     128 

79.  Reynier's  incandescent  lamp,  with  globe  .....  128 

80.  Chandelier  of  Weraermann  lamps        ......     129 

81.  Reynier's  latest  form  of  incandescent  lamp  ....  130 

82.  Reynier  automatic  lighter         ...  ...    131 

83.  Arrangement  of  parts  and  electrical  connection  of  the  automatic  lighter         131 


LIST   OF  ILLUSTRATIONS.  xv 

FIG.  PAGE 

84.  Reynier  system  of  distribution     .  .  .  .  .  .132 

85.  Temporary  regulator  of  Reynier,  serving  as  a  safety-lamp,  in  electric 

installations  .  .  .  .  .  .  .  .133 

86.  Incandescent  lamp,  with  rotating  electrode,  of  M.  Ducretet      .  .  134 

87.  Incandescent  lamp  of  M.  Ducretet     ......     134 

88.  Section  of  M.  Ducretet's  lamp 135 

89.  M.  Clamond's" incandescent  lamp        .  .  .  .  .  .135 

90.  Sawyer's  incandescent  lamp  in  an  atmosphere  of  nitrogen        .  .  136 

91.  Vertical  section  of  the  lamp-soleil      .  .  .  .  .     141 

92.  Lamp-soleil  suspended,  perspective  view  ....  143 

93.  Entrance  to  the  passage  Jouffroy,  in  Paris,  lit  by  the  lamp-soleil    .  .     146 

94.  Thomas  A.  Edison 149 

95.  Sketch  of  Edison's  first  lamp.     (From  his  French  patent.) .  .  .     152 

96.  Edison  lamp  with  incandescent  platinum  spiral,  provided  with  safety 

apparatus.    (French  patent,  1879.)    .  .  .  .  .  153 

97.  Edison's  platinum-lamp,  with  regulator  operated  by  expansion  of  heated 

air 154 

98.  Edison  lamp  with  Bristol-board  carbon,  according  to  his  French  patent 

1  of  May  28,  1879 157 

99.  Edison's  carbon-lamp  with  spiral  filament.     (American  patent,  January 

27,  1880.) 158 

100.  Lamp  with  horse-shoe  filament    .  .  .  .  .  .159 

101,  102,  103,  104.  The  actual  Edison  lamps         » 160 

105.  Edison  lamp  provided  with  regulator  of  intensity          .  .  .  161 

106.  Carbon-rod  rheostat  of  the  regulator  of  intensity     ....  161 

107.  Sixteen-candle  lamp  (three-quarter  size) .  .  .  .  .  162 

108.  Crystal  chandelier  of  Edison  lamps,  used  at  the  Paris  Exposition  of  Elec- 

tricity        .-          .  .  *  .  .  .  .  .    163 

109.  Edison  lamp  with  shade    .  .  .  .  .  .  .164 

110.  Jointed  bracket  for  Edison  lamp        .  .  .  .  .  .     165 

111.  Edison  three-light  chandelier       .  ....  .  .  166 

112.  Parlor  in  New  York  lighted  with  Edison  lamps       .  .  .  .168 

113.  Edison  mining-lamp          .  .  .  .  .  .  .169 

114.  Swan  incandescent  lamp          .  .  .  .  .  .172 

115.  Swan  table-lamp     ........  173 

116.  Under  side  of  the  foot  of  the  lamp,  showing  the  electrical  connections      .     174 

117.  Swan  lamp.     Later  form  ...  .*,-.          .  .  .  174 

118.  Swan  lamp  in  socket    .  ..         .  .  ....    174 

119.  Philosophical  instrument  establishment  of  Mr.  Swan,  at  Newcastle,  light- 

ed by  his  incandescent  lamps  .  .  .  .  .  175 

120.  Swan  mining-lamp       .  .  ,  .  .  .  .  .176 

121.  Lane-Fox  incandescent  lamp        .  .....  177 

122.  Section  of  Lane-Fox  lamp       .  .  _v  .  .  .  .     178 

123.  Maxim  incandescent  lamp.     (Full  size.)  .  .  .  .  179 

124.  Maxim  incandescent  lamp  and  socket.     (Full  size.) ....     180 

125.  The  Bernstein  lamp  .  .  .  .  .  .  .  181 

126.  Wheatstone's  bridge     .  ...  .  .  .  .     182 

127.  Bunsen  photometer  .  .  .  .  .  .  183 

128.  Method  of  using  the  Bunsen  photometer       .....    184 

129.  Daniell  battery       ........  200 

130.  Reynier  battery  ....  ,200 


xvi  LIST  OF  ILLUSTRATIONS. 

FIG.  PAGE 

131.  Bunsen  battery      ........  201 

132.  Small  model  of  the  circular  form  of  the  Reynier  battery     .            .            .  202 

133.  Thermo-electric  pile  of  Clamond  ......  209 

134.  Experiment  of  Faraday  with  two  bobbins     .....  212 

135.  Experiment  of  Faraday  with  a  bobbin  and  magnet        .            .            .  213 

136.  Ruhmkorff  coils  .  .  .  .  .  .  .216 

137.  The  Ruins  of  the  Coliseum  at  Rome  illuminated  by  the  electric  light  219 

138.  Magneto-electric  machine        .......  220 

139.  Separately  excited  dynamo           ......  220 

140.  Series  dynamo 221 

141.  Shunt  dynamo        ........  221 

142.  Faraday's  apparatus     ........  224 

143.  Direct  induction  in  the  ring  armature     .....  229 

144.  Indirect  induction,  or  induction  by  magnetic  reaction  of  the  radiating 

armature-cores.      ........  230 

145.  Magneto-electric  machine  of  Pixii,  1832  .....  232 

146.  Magneto-electric  machine  of  Clarke  ......  233 

147.  Experiments  in  the  projection  of  the  electric  light  at  London,  on  the 

Thames,  with  a  Brush  lamp  of  six  hundred  carcels             .            .  235 

148.  Siemens  armature 237 

149.  Cross-section  of  the  Siemens  armature     .....  237 

150.  Wilde's  first  dynamo-electric  machine,  with  Siemens'  magneto-electric 

exciter 238 

151.  Gramme  magneto-electric  machine  for  the  laboratory  .            .            .  241 

152.  First  form  of  Gramme  dynamo  machine  for  lighting           .            .            .  242 

153.  Gramme  machine.     (Workshop-type.)      .            .            .            .            .  243 

154.  Gramme  ring    .........  244 

155.  Five-light  Gramme  machine         ......  246 

156.  Diagram  of  alternating-current  Gramme  machine    ....  250 

157.  Self-exciting  alternating-current  Gramme  machine        .            .            .  251 

158.  M.  Gramme      .....  .  .  .  .252 

159.  Armature  of  the  Wood  machine  ......  252 

160.  Cross-section  of  the  Wood  armature  ......  253 

161.  Gramme  machine  as  modified  by  Mr.  Wood       ....  254 

162.  Original  model  of  the  Pancinotti  machine,  exhibited  at  the  Exposition  of 

Electricity  at  Paris,  1881  .  .  .  .  .  .  .256 

163.  Siemens  continuous-current  machine.     (Vertical  model.)          .            .  258 

164.  Mansion-House  Square,  London,  lighted  by  Siemens'  lamps           .            .  259 

165.  Diagram  of  the  winding  of  the  Heffner  von  Alteneck  drum     .            .  261 

166.  Diagram  of  the  connection  of  the  coils          .....  261 

167.  Alternating-current  machine  of  Heffner  von  Alteneck  .            .            .  262 

168.  Diagram  of  armature  and  field  coils  of  Ferranti  machine    .            .            .  263 

169.  Gordon  alternating-current  dynamo        .....  264 

170.  Weston  dynamo 265 

171.  Weston  armature 266 

172.  Core  of  Weston  armature        .......  267 

173.  Toothed  iron  disk  used  in  Weston  armature       ....  267 

174.  Maxim  dynamo-electric  machine  for  lighting,  with  double  ring  and  two 

commutators          ........  268 

175.  Maxim  exciting-machine  with  automatic  current  regulator.   (Front  view.)  270 

176.  Maxim  exciting-machine  with  current  regulator.    (Side  view.)            .  271 


LIST  OF  ILLUSTRATIONS.  xvii 

FIG.  PAGE 

177.  Edison  machine  .  .  .  .  .          ..•"'•  .274 

178.  Edison  steam  dynamo       .            .            .    '        .            .            .            .  275 

179.  Construction  of  the  armature  of  the  Edison  steam  dynamo             .  '         .  276 

180.  Art-gallery  in  New  York  lighted  by  Edison  incandescent  lamps          .  278 

181.  Brush  sixteen-light  machine   .  *         .» -        '   .           V           .            .            .  280 

182.  Cross-section  of  the  Brush  ring    .            .            .            .            .            .  281 

183.  Construction  of  the  Brush  ring          .            .            .            »•'           .            .  281 

184.  Brush  armature,  with  its  coils  in  position           .            ,            .            .  282 

185.  Cross-section  of  Brush  commutator   .            .-           /           .            .-'           .  283 

186.  Diagram  of  Brush  dynamo        •    .            .            .            .            .            .  284 

187.  Wallace-Farmer  machine        .            .            .            .            .          '  v            .  287 

188.  Armature  of  the  Lontin  continuous-current  machine    .            .            .  288 

189.  Drum-armature  of  the  Biirgin  machine         .....  290 

190.  Magneto-electric  machine  of  M.  de  Meritens.     (Light-house  type.)      .  292 

191.  Details  of  the  De  Meritens  armature  .  .  .  .  .  .293 

192.  Diagram  of  the  De  Meritens  armature  coils        .            .            .            .  293 

193.  Magneto-electric  machine  of  M.  de  Meritens.     (Workshop-type.)    .            .  294 

194.  M.  de  Meritens's  continuous-current  magneto-electric  machine            .  295 

195.  Details  of  the  ring  of  continuous-current  machine  of  M.  de  Meritens         .  296 

196.  Gravier's  plumbago  commutator-brushes            .            .            .            .  297 

197.  Plan  of  the  electric-lighting  system  of  the  port  of  Havre    .            .            .  318 

198.  Diagram  of  one  of  the  circuits  in  the  electric-lighting  of  the  port  of  Havre  320 

199.  Junction-box          .            .            .            .            ...            .  323 

200.  View  of  the  port  of  Havre  lighted  by  Jablochkoff  candles.          Face  page  324 

201.  Lane-Fox's  regulator  of  current  intensity     .....  327 

202.  Diagram  of  Edison  street-mains  .            .            .           •,                        .  328 

203.  Edison  junction-box,  with  fusible  safety-catch,  for  street-mains     .            .  329 

204.  Edison  junction-box,  with  safety-catch,  for  connection  of  service-wires 

with  mains       .            .            .            .            .            .            .            .  330 

205.  Safety-plate  with  fusible  cut-off,  placed  at  points  where  the  wires  enter  a 

house          .  .  .  .  .  .          ..  ;  .331 

206.  Lamp-socket  with  safety-catch     .            .            .           -.                    '••  '.  332 

207.  View  from  below  of  the  lamp-base     .            .            .            ...  332 

208.  M.  Gravier's  system  of  electrical  distribution  at  the  Zawiercie  works, 

Poland .           ..  334 

209.  M.  Gravier's  regulator             .            .            .            ...           .  336 

210.  Rheometric  regulator  of  M.  Gravier         .            .            .            .            .  337 

211.  Music-hall  on  the  Place  du  Chateau-d'Eau,  in  Paris,  lighted  by  Jabloch- 

koff candles  .  .  .  .  .  .  .  .339 

212.  Marcel  Deprez  winding  for  constant  electro-motive  force         .           .  340 

213.  Marcel  Deprez  winding  for  constant  current             .            .          ,.            .  341 

214.  Arrangement  of  dynamos  for  the  distribution  of  electricity  on  the  system 

of  M.  Marcel  Deprez    .......  342 

215.  Professor  Perry's  machine  for  constant  electro-motive  force           .            .  344 

216.  Professor  Perry's  machine  for  constant  current          ~  .            .            .  345 

217.  Edison  dynamo  with  compound  winding,  for  constant  electro-motive 

force  .-  .  .  ....  .  .346 

218.  Diagram  of  the  Edison  automatic  regulator       .            .            .            .  348 

219.  Edison  automatic  regulator    .            .            .            .            .            .            .  349 

220.  Weston  automatic  regulator  for  arc-lighting      .            ,            .            .    .  351 

221.  Details  of  the  Weston  automatic  regulator    .  i  .  .  .352 

2 


xviii  LIST  OF  ILLUSTRATIONS. 

FHJ.  PAGE 

222.  Brush  automatic  regulator           ......  353 

223.  Edison  multiple-series  distribution    ......  356 

224.  Edison  multiple-series  distribution  applied  to  one  generator    .            .  357 

225.  Edison  meter    .........  3G4 

226.  Edison  meter,  with  registering  apparatus  *         ....  366 

227.  Mr.  Boys'  work-meter .            .            .            .            .            ...  368 

228.  Electric  light-house  of  Planier,  near  Marseilles  .            .            .            ,  379 

229.  Arrangement  of  the  Planier  electric  light-house       ....  381 

230.  Section  of  the  upper  story  and  lantern  of  the  Planier  light-house        .  382 

231.  Fixed  light  electric  light-house           ......  385 

232.  Factory  of  MM.  Sautter  and  Lemonnier  lighted  by  the  electric  light  .  387 

233.  M.  Menier's  yacht,  with  electric  projector,  navigating  the  Marne  by  night  391 

234.  Mangin  projector         ........  395 

235.  Mangin  projector,  with  its  accessories,  mounted  upon  the  field-wagon  397 

236.  Portable  apparatus,  with  Brotherhood  engine  and  Gramme  machine,  for 

use  with  Mangin  projector     .....  Face  page  398 

237.  The  Surveillante  lighting  the  island  of  Tabarka  for  the  first  descent  of 

the  French  troops  upon  Tunis     ......  400 

238.  Apparatus  used  in  "  The  Prophet,"  to  represent  the  sun           .            .  408 

239.  Apparatus  for  the  production  of  the  rainbow  on  the  stage  .            .            .  409 

240.  The  rainbow  in  the  opera  of  "  Moses  "     .            .            .            .            .  410 

241.  Magic  mirror  for  the  production  of  lightning  in  the  theatre  .  .411 

242.  Electric  lamp  for  illuminating  an  actor  in  the  play       .            .            .  412 

243.  Electric  lamp,  with  mirror,  for  lighting  a  particular  point  of  the  scene     .  412 

244.  Scene  in  the  opera  of  "  Moses "     .            .            .            .            .            .  413 

245.  Luminous  fountain      ........  414 

246.  Electric  lighting  of  the  fast-freight  room  of  the  Paris  depot  of  the  Paris, 

Lyons,  and  Mediterranean  Railroad.     (Lontin  system.)      .            .  422 

247.  Electric  lighting  of  an  open  space      ......  425 

248.  Farm-work  carried  on  by  means  of  the  electric  light     .            .  Face  page  425 

249.  Electric  lighting  of  the  work  on  the  Kehl  bridge     ....  426 

250.  Plate  reflector 430 

251.  Lighting  of  the  Boulevard  des  Italiens  by  the  Million  lamp           .           .  436 


BOOK    I. 
HISTORY   OF   ARTIFICIAL    LIGHTING. 


CHAPTER  I. 

OILS,   CANDLES,  AND   GAS. 

To  acquire  a  real  comprehension  of  the  true  role  of  the 
electric  light  and  the  changes  which  it  can  introduce  both  in 
our  habits  and  in  the  industrial  world,  it  is  necessary  to  give 
succinctly  the  history  of  lighting  in  general,  and  of  electric 
lighting  in  particular. 

Fats  and  oleaginous  materials  were  employed  as  a  means 
of  lighting  by  the  most  ancient  peoples.  But,  even  among 
the  most  civilized  nations  of  antiquity,  such  as  the  Greeks 
and  Romans,  this  mode  of  lighting  had  preserved  nearly  as 
barbarous  a  form  as  among  the  savage  tribes.  The  lamp  of 
a  Roman  emperor  was  not  much  pleasanter  or  less  smoky 
than  the  torch  of  resinous  wood  with  which  the  first  known 
men  lighted  their  abodes — those  men  whom  history  ignores, 
and  whom  geology  has  resuscitated  during  the  last  twenty- 
five  years. 

This  lamp  consisted  simply  of  a  vessel  filled  with  oil,  into 
which  dipped  a  thick,  twisted  wick,  formed  of  any  fibrous 
material,  wool,  linen,  cotton,  etc.  The  end  of  this  wick  was 
raised  so  as  to  rest  on  the  edge  of  the  vessel,  and  it  was  there 
that  the  oil  burned,  creeping  up  through  the  wick  by  capil- 
larity (Fig.  2). 

Specimens  of  these  apparatus  can  still  be  seen  elsewhere 
than  in  museums.  The  peasants  of  other  countries  have  pre- 
served the  classic  lamp  up  to  our  days,  perfecting  a  little  the 
burner,  or  neck,  to  prevent  the  wick  from  falling  back  into 
the  oil.  As  a  regulator  to  advance  this  wick  as  fast  as  it  was 
burned,  the  Roman  matron,  as  well  as  the  peasant's  wife  of 
to-day,  had  doubtless  no  better  arrangement  than  a  common 


2  HISTORY  OF  ARTIFICIAL  LIGHTING. 

hair-pin ;  for  the  pincers  and  hook  specially  made  for  this 
purpose  resembled  one  in  shape,  and  were  but  little  more 
convenient  (Figs.  1  and  3). 

This  thick  wick,  or,  we  should  rather  say,  this  string  of 
tow,  does  not  permit  the  air  to  penetrate  sufficiently  to  burn 
completely  the  carbon  of  the  oil.  The  unburned  carbon 
escapes  in  a  nauseous  smoke,  which  produces  a  choking 
sensation.  But  the  smoke  of  ancient  times  must  have  been 
much  worse  than  that  of  to-day,  because  the  oil  was  very 
impure,  and  was  often  replaced  by  fats  full  of  all  kinds  of 
impurities.  We  give  here  illustrations  of  the  lamp  which 
figures  in  the  most  poetical  stories  of  Greece.  We  may  see 
in  it  the  elegant  lamp  which  the  imprudent  Psyche  over- 


Fio.  1.— Pincers  FIG.  2.— Bronze  Koinan  lamp.  FIG.  3.— Hook 

for  lamp.  for  lamp. 

turned  upon  Cupid  on  that  fatal  night  when  she  yielded  to 
the  ill-fated  desire  of  unveiling  the  incognito  of  her  myste- 
rious lover.  We  can  understand  the  anger  of  the  divine 
child,  which,  in  the  case  of  the  little  electric  burner,  would 
be  inexplicable.  In  this  last  case,  even  if  he  were  to  be 
burned,  he  would  need  no  perfumes  to  disinfect  himself. 

In  the  sumptuous  palaces  of  imperial  Rome,  as  well  as  in 
the  hovel  of  the  slave  situated  in  the  remotest  fields,  the  sys- 
tem of  lighting  was  everywhere  the  same.  It  was  easy  to 
substitute  for  coarse  earthenware  precious  metals  for  making 
the  lamp,  to  give  ifc  an  elegant  form,  and  support  it  on  can- 
delabra, richly  sculptured  (Figs.  4  and  5)  and  designed  with 
skill ;  but  it  is  always  the  same  lamp  which  we  have  to  de- 


OILS,   CANDLES,   AND   GAS. 


scribe — its  luxurious  appearance  could  not  modify  its  organi- 
zation in  any  essential. 

Many  savants  to-day  consider  fire,  as  well  as  language,  to 
be  the  great  characteristic  of  humanity.  It  is  singular  that  this 
primordial  invention,  which  has  made  man  the  superior  of  all 
that  is  highest  in  nature,  and  has  taken  him  out  of  the  rank 
of  animal,  has  been  one  of  the  last  to  be  perfected.  Yet  this 
is  precisely  what  has  happened.  The  Roman  lamp,  scarcely 
superior  to  the  utensils  of  the  primitive  savages,  remained 
without  a  rival  during  the  greater  part  of  the  middle  ages. 


FIGS.  4  aiid  5. — Eoman  candelabra  in  carved  bronze,  bearing  one  or  more  lamps. 

Only  at  the  end  of  the  twelfth  century  did  the  great  nov- 
elty dawn  upon  England — a  light-giving  solid  material  to  re- 
place oil.  This  novelty  had  for  name  the  "  tallow-candle  "! 
It  was  made  of  sheep' s  fat,  and  of  the  well-known  form  which 
it  has  preserved  to  the  present  day.  It  may  have  seemed  a 
dangerous  invention,  because  it  took  a  long  time  for  its  use 
to  extend  itself.  It  was  in  the  reign  of  Charles  V,  at  the  end 
of  the  fourteenth  century,  that  the  French  began  to  use  it. 
I  refer  to  the  rich  men  of  France ;  it  was  as  yet  too  great  a 
luxury  for  the  commonalty  to  indulge  in. 


4  HISTORY  OF  ARTIFICIAL  LIGHTING. 

To  our  fathers  it  seemed  a  great  step  in  advance — and  for 
their  epoch  they  were  right — and  they  were  contented  with 
it  for  a  long  time.  Le  roi  soleil  had  no  other  luminaries  to 
light  up  at  night  the  glories  of  Versailles,  and  the  plays  of 
Moliere,  of  Racine,  and  even  those  of  Voltaire,  were  produced 
by  the  light  of  candles  of  six  to  the  pound. 

For  a  long  time,  also,  those  traveling  through  the  streets 
of  the  cities  were  most  happy  to  be  guided  on  their  way  by 
the  light  of  candles  placed  in  the  corners  of  the  windows. 
Lanterns  for  public  lighting  date  from  the  middle  of  the 
seventeenth  century  only ;  and  it  is  not  until  a  hundred  years 
later  that  we  find  them  surmounted  by  a  reflector,  depriving 
the  sky  of  their  slender  rays  in  order  to  cast  them  back  upon 
the  earth.  It  was  then  that  they  assumed  the  well-known 
name  of  reflectors  (reverberes).  Some  among  us,  who  have 
passed  the  critical  time  of  youth,  can  remember  them  dang- 
ling from  the  altitude  of  a  gallows-frame,  whence  they  de- 
scended at  the  end  of  a  cord,  like  a  bucket  into  a  well,  when 
it  was  necessary  to  light  or  to  extinguish  them. 

To-day  the  tallow-dip  has  developed  into  the  candle. 
Thanks  to  the  discovery  of  the  composition  of  fatty  bodies, 
made  by  Chevreul  in  1811,  it  became  possible  to  extract  from 
tallow  the  best  of  its  luminiferous  components,  stearic  acid. 
M.  Chevreul  himself  tried  it  in  conjunction  with  Gay-Lussac, 
and  the  two  took  out  in  Paris  a  patent  for  the  process,  which, 
however,  was  never  used,  any  more  than  the  English  patent 
taken  out  in  London  by  Gray-Lussac  under  the  name  of  Moses- 
Poole.  We  must  not  forget,  however,  that  their  method 
could  not  work  in  practice. 

Another  chemist,  Cambaceres,  took  out  four  patents  for  the 
same  object  during  the  years  1825  and  1826.  He  was  somewhat 
more  fortunate  than  his  illustrious  competitors,  and  was  the 
first  to  manufacture  stearine-candles,  undoubtedly  very  imper- 
fect and  very  impure,  as  their  yellow  coloration  plainly  showed. 
These  candles  soiled  the  hands  like  the  tallow-dips,  smelled 
almost  as  bad,  and  burned  in  an  inferior  manner  in  spite  of 
the  perfecting  of  the  wick.  For  these  reasons  their  sale  was 
very  limited,  and  Cambaceres  soon  gave  up  the  manufacture. 

It  was  two  young  physicians,  MM.  de  Milly  and  Matard, 
who  took  up  the  problem  in  1829,  and  reached  at  last  a  satis- 
factory solution  after  two  years  of  patient  research.  Thus  it 
is  in  the  year  1831  that  the  history  of  the  manufacture  of 


OILS,   CANDLES,   AND   GAS.  5 

stearine-candles  begins,  and,  as  the  first  factory  was  situated 
near  the  Arc  de  Triomphe  de  1'Etoile,  they  were  named  bou- 
gies de  Vetoile  (star- can  dies),  soon  known  throughout  the 
world,  which  name  they  kept  when  the  factory  was  moved 
away  from  that  place. 

More  solid  and  better  in  appearance,  as  well  as  less  greasy 
to  the  touch,  and  provided  with  a  wick  which  needed  no 
snuffing,  because  it  burned  itself  up,  burning  without  smoke 
or  disagreeable  odor,  the  stearine- candle  preserved  the  form 
of  the  old  tallow- dip,  and,  from  the  physical  point  of  view, 
worked  in  the  same  manner.  But  it  also  gave  more  light. 
It  is  it  which  will  hereafter  be  employed  as  a  standard  in 
comparing  sources  of  light,  a  candle  being  taken  as  such 
standard  which  burns  ten  grammes  of  stearine  per  hour— 
unfortunately,  a  unit  which  varies  greatly  according  to  the 
greater  or  less  purity  of  the  stearine  employed  in  commerce. 

The  "  star- candles  "  then  sold  for  three  francs  fifty  cen- 
times a  kilogramme,  so  that  the  standard  candle,  burning  ten 
grammes  per  hour,  costs  three  and  a  half  centimes  for  one 
hour's  burning.  On  account  of  a  lower  price,  it  now  costs 
little  over  two  centimes.  On  the  other  hand,  it  is  much 
dearer  than  the  tallow-candle,  which  formerly  did  not  bring 
half  the  price  of  the  stearine- can  die,  and  which  to-day  is 
worth  far  less,  in  the  proportion  of  one  franc  twenty-five 
centimes  to  two  francs  ten  centimes  a  kilogramme.  It  is  true 
that  a  kilogramme  of  tallow  gives  only  four  fifths  as  much 
light  as  the  same  quantity  of  stearine.  But,  taking  this  dif- 
ference into  account,  the  expenses  will  be  found  not  to  exceed 
one  centime  and  a  half  per  hour  and  per  unit  of  light ;  that  is 
to  say,  hardly  three  quarters  of  the  cost  of  the  stearine-candle 
for  the  same  result. 

Hence  the  new  candle  has  only  been  an  advance  from  the 
point  of  view  of  comfort  and  luxury,  but  not  from  the  stand- 
point of  economy.  The  same  does  not  apply  to  another  in- 
vention, which  has  transformed  the  conditions  under  which 
oil  is  employed — we  speak  of  the  modern  lamp. 

The  end  of  the  eighteenth  century  was  marked  by  a  dis- 
covery which  produced  upon  the  public  as  great  an  effect  as 
that  of  the  electric  light  to-day.  This  discovery,  whose  name 
now  sounds  even  vulgar  to  us  on  account  of  its  very  popu- 
larity, is  the  Argand  lamp.  We  shall  now  show  how  it  has 
transformed  the  ancient  Roman  lamp. 


6  HISTORY  OF  ARTIFICIAL  LIGHTING. 

If  the  lamp  with  thick  wick  gives  so  much  smoke  and  so 
little  light,  it  is  because  enough  air  does  not  get  access  to  it 
to  supply  the  oxygen  necessary  for  the  complete  combustion 
of  the  carbon.  The  light  being  produced  by  the  combustion, 
it  is  much  less  vivid,  just  like  the  combustion  itself.  On  the 
other  hand,  the  flame,  full  of  particles  of  carbon  which  have 
not  found  molecules  of  oxygen  to  unite  with  in  legitimate 
marriage,  has  not  enough  heat  to  bring  all  to  the  temperature 
where  they  become  luminous.  It  remains,  then,  charged  with 
black  particles — that  is  to  say,  with  smoke — which  obscures  it 
and  fills  it  with  all  the  odors  that  can  be  produced  from  the 
oil,  odors  which  a  more  complete  combustion  would  have  de- 
stroyed. 

To  suppress  all  these  troubles  a  greater  influx  of  oxygen 
upon  the  flame  must  be  contrived.  To  do  this,  Argand  had 
the  idea  of  giving  to  the  wick  the  form  of  a  cylindrical  tube, 

and  allowing  the  air  to  penetrate  to  its 
center.  The  flame  no  longer  formed  a 
solid  cylindroid  like  that  of  a  candle, 
but  a  circular  plane,  quite  thin,  and 
well  supplied  on  both  sides  with  air,  so 
that  it  no  longer  was  in  want  of  oxy- 
gen. The  reservoir  of  oil  was  placed 
at  a  certain  distance  from  the  burner, 
and  in  a  somewhat  more  elevated  posi- 
tion, so  that  the  fluid  would  rise  to  the 
level  of  the  wick,  in  accordance  with 
the  laws  of  equilibrium  in  communi- 
6.-Quinquet's  lamp  hung  catinS  vessels.  The  apparatus  divided 
upon  a  wail.  thus  into  two  parts,  and  united  by  a 

communicating  tube,  was  fastened  to 

a  wall  (Fig.  6),  or  it  rested  on  a  rod  or  flat-footed  standard 
of  some  degree  of  stability. 

To  this  new  disposition  of  parts  Quinquet  added  a  chimney 
of  glass,  which  increased  the  draught — that  is  to  say,  increased 
the  quantity  of  air  supporting  the  flame — and  he  produced  the 
complete  invention  under  his  own  name  in  1785.  This  date 
is  of  as  much  importance  in  artificial  lighting  as  is  1789  in 
politics.  It  was  the  epoch,  in  effect,  of  a  complete  industrial 
revolution.  Between  the  ancient  lamps  and  the  lamp  of 
Quinquet  there  is  as  much  difference  as  between  the  chimney 
of  our  parlors  and  the  fireplace  of  our  original  Aryan  ances- 


OILS,   CANDLES,   AND  GAS. 


tors,  formed  by  a  hole  dug  in  the  ground  in  the  center  of  their 
cabins. 

Later,  Carcel  excited  a  universal  enthusiasm  in  adapting 
to  Quinquet's  lamps  a  clock-movement — replaced  at  a  more 
recent  period  by  a  spring — and  moving  by  it  a  piston  which 
pressed  upon  the  oil  and  forced  it  to 
rise  in  the  wick  in  greater  quantity. 
This  made  it  possible  to  place  the 
oil-reservoir  below  the  wick,  and  the 
flame  could  be  given  a  brightness 
which  surpassed  all  expectations 
(Fig.  7).  Louis  XIV  would  have 
been  dazzled  by  it. 

Carcel's  invention,  giving  to  the 
light  of  the  lamp  more  regularity 
than  the  candle  possessed,  furnishes 
us  with  a  new  unit  for  comparing 
sources  of  light,  and  for  measuring 
their  illuminating  power.  The  con- 
ditions under  which  the  type  of  lamp 
adopted,  called  the  Carcel,  should 
burn,  have  been  determined,  and 
have  been  expressed  in  the  practi- 
cal directions  drawn  up  in  1860  by 
MM.  Dumas  and  Regnault  for  the 
daily  tests  of  the  illuminating  power 
of  the  Paris  gas.  The  wick  should 
be  three  centimetres  in  diameter, 
and  the  lamps  should  burn  forty- 
two  grammes  of  purified  colza-oil, 
with  a  flame  four  centimetres  in 
height.  Compared  with  the  different  standard  candles  adopted 
elsewhere,  the  Carcel  lamp  equals  seven  and  a  half  stearine- 
candles,  those  which  are  called  "  star-candles,"  and  which  are 
still  used  in  France  for  minor  illumination.  For  the  sper- 
maceti-candle employed  in  England,  or  "standard  candle" 
a  Carcel  lamp  is  equal  to  seven  and  four-tenths  candles.  For 
the  paraffine-candle  used  in  Germany,  a  Carcel  burner  equals 
nine  and  six  tenths  candles. 

The  Light-house  Board  of  France  had  adopted  a  somewhat 
lower  type,  burning  only  forty  grammes  of  purified  colza-oil 
per  hour.  But  the  Congress  of  Electricians,  without  arriving 


FIG.  7. — Lamp  of  the  Carcel  type, 
with  moderator  mechanism,  and 
bottom  oil-reservoir. 


8  HISTORY  OF  ARTIFICIAL  LIGHTING. 

at  an  absolute  decision  as  regards  photometric  standards,  has 
expressed  the  desire  that  all  experiments  should  be  conducted 
upon  the  uniform  type  of  forty-two  grammes ;  in  other  words, 
with  the  Paris  standard. 

Taking  the  price  of  oil  at  one  franc  and  fifty  centimes  a 
kilogramme,  the  expense  of  a  Carcel  lamp  is  six  and  three 
tenths  centimes  per  hour,  while  eight  candles  for  the  same 
space  of  time  would  cost  seventeen  centimes.  Lighting,  there- 
fore, is  three  times  cheaper  with  the  Carcel  lamp  than  with 
candles.  At  the  same  time  the  light  is  whiter,  more  regular, 
and  also  more  concentrated,  so  that  a  greater  luminous  in- 
tensity can  be  obtained.  Thus  the  lamp  appears  from  all 
points  of  view  an  advance  upon  the  candle  and  tallow-dip. 

The  modern  lamp,  which  we  use  to  the  present  day,  was  a. 
completed  invention.  But,  just  as  it  took  its  final  form,  it 
found  ready  for  it  a  rival  which  has  rapidly  replaced  it  for  all 
extended  uses. 

Before  the  year  1801  the  French  engineer  Lebon  had  dis- 
covered and  demonstrated  the  powerful  lighting  qualities  of 
gas  produced  by  the  distillation  of  bituminous  coal  in  closed 
vessels.  But,  as  often  happens,  the  idea  originating  in  France 
was  at  first  only  applied  in  England.  In  France,  gas  was  pro- 
nounced unhealthy,  just  as  coal  itself  had  been  for  the  same 
reason  condemned  a  short  time  before.  Nevertheless,  it  was 
tried  in  Paris  in  1818,  under  the  administration  of  M.  de 
Chabrol,  and  its  immense  success  immediately  forced  it  into 
the  public  service ;  after  having  conquered  the  streets,  the 
conquering  hero  soon  penetrated  also  the  private  houses,  and 
was  accepted  everywhere. 

It  is  this  light  that  reigns  to-day,  and  its  supremacy  is  due 
principally  to  its  cheapness.  A  gas-flame  equal  to  the  Carcel 
]amp  only  costs  at  Paris  three  centimes  per  hour,  instead  of 
six  and  a  half ;  that  is  to  say,  less  than  half  the  cost  of  oil. 
This  calculation  is  based  on  a  high  price  for  gas,  such  as  still 
obtains  in  some  situations,  namely,  thirty  centimes  per  cubic 
metre  ($1.70  per  1,000  feet).  But  in  the  case  of  cities,  which 
pay  only  fifteen  centimes,  the  expense  comes  down  to  one 
quarter  the  cost  of  oil,  and  this  is  the  price  all  consumers  pay 
in  London,  as  well  as  in  most  English  cities. 

The  producers  of  oil  believed  that  they  had  received  a 
death-blow,  and,  as  bituminous  coal  as  well  as  oil  was  a  home 
product,  they  could  not  suppress  the  new  industry  by  a  pro- 


OILS,   CANDLES,   AND   GAS.  9 

tective  tariff.  Gas  gave  more  light  for  less  money,  could  be 
conveniently  used  in  all  places,  and  did  away  with  a  lot  of 
utensils  which  were  always  a  source  of  trouble  and  uncleanli- 
ness.  How  could  such  a  rival  be  conquered  ? 

Natural  as  these  pessimistic  forebodings  seemed,  expe- 
rience has  proved  their  falsity.  The  oil  industry  is  as  pros- 
perous to-day  as  it  ever  was.  Its  production  has  not  dimin- 
ished. By  the  side  of  the  brilliant  triumphs  of  gas,  it  has 
filled  many  places  where  the  new  conqueror  could  find  no  foot- 
ing, and  in  these  cases  the  original  consumption  of  oil  has  been 
increased,  because  the  eye,  more^  exacting  ojx-accaunt  of  the 
prodigal  light  of  gas,  is  not  content  with  the  feeble  light  which 
formerly  satisfied  it.  Thus,  what  ,the  lamp  has  lost  by  com- 
petition with  gas,  it  has  gained  in  the  competition  with  the 
candle,  in  spite  of  the  transformation  of  the  latter  into  a  clean J 
er  and  better  luminary  than  it  was  of  old. 

About  1860  the  discovery  of  petroleum  added  still  more  to 
our  resources,  giving  us  a  light  at  least  as  good  as  that  of  gas 
at  a  much  lower  price,  yet  we  (the  French)  were  the  only  ones 
who  were  not  allowed  to  profit  by  the  discovery,  because  of 
the  heavy  tariff  which  the  oil  had  to  pay  on  its  entry  into 
France.  Again,  the  oil-producers,  and  even  the  gas-manu- 
facturers, felt  themselves  seriously  menaced.  Nevertheless, 
gas  continues  to  prosper,  not  only  in  France,  but  also  in 
England  and  Germany,  where  petroleum  costs  twenty  cen- 
times a  litre,  and  even  in  New  York,  where  it  hardly  costs 
two  centimes,*  on  account  of  the  proximity  of  the  Pennsyl- 
vania wells. 

What  has  been  going  on  for  the  last  fifty  years  between 
oil  and  gas  is  taking  place  to-day  between  gas  and  electricity. 
Since  the  electric  light  has  grown,  and  seems  to  threaten  the 
domain  of  gas,  all  the  interests  there  engaged  are  trembling, 
as  the  representatives  of  oil  did  of  old.  Already  it  has  sev- 
eral times  happened  that  the  announcement  of  such  or  such 
an  electrical  discovery  has  induced  real  panics  among  the 
numerous  stockholders  of  the  gas  companies  of  the  world, 
especially  those  of  America. 

These  fears  are  without  foundation :  the  coming  of  the 
electric  light  will  create  new  needs ;  without  injuring  con- 

*  [This  price  is  about  two  cents  a  gallon.  Petroleum  suitable  for  burning  in 
lamps  can  not  be  bought  in  New  York  by  the  barrel  at  less  than  seven  times 
this  price.] 


10 


HISTORY  OF  ARTIFICIAL  LIGHTING. 


temporaneous   industries,  it  will   cause   improvements,  and 

probably  a  lowering  in  price,  by  which  the  whole  community 

will  profit. 

The  consumer  will  spend  just  as  much  money,  but  will 

have  a  better  light,  and  the  producer  will  make  his  profit  on 

an  increased  sale.  Of  this 
we  have  already  seen  the 
proof  in  the  improvements 
recently  introduced  in  gas- 
burners,  in  which  the  illu- 
minating power  has  been  in- 
creased and  the  consump- 
tion of  gas  diminished  in  a 
ratio  that  four  or  five  years 
ago  would  have  seemed  in- 
credible. 

As  for  coal,  it  is  not  at 
all  menaced,  because  it  is 
by  the  intermediation  of  the 
steam-engine,  that  is  to  say, 
by  the  consumption  of  coal, 
that  electricity  is  produced. 
It  may  be  that  in  some  con- 
ditions gas-engines  may  be 
employed  instead  of  steam- 
engines,  so  that  gas  will 
profit  by  the  development 
of  electricity. 

Here  we  must  speak  of 
two  other  processes  of  light- 
ing which  are  interesting,  be- 
cause the  principle  of  incan- 
descence on  which  they  are 
founded  is  applied  with  suc- 
cess in  certain  recent  systems 
of  electric  lighting,  and  be- 
cause they  give  us  very  pow- 
erful lights,  comparable  from 
this  point  of  view  with  the 


FIG.  8. — Lamp  of  M.  Tessie"  du  Motay  for  pro- 
duction of  the  Drummond  light. 

A  and  B,  inlet- cocks  for  oxygen  and  coal  gas, 
brought  through  caoutchouc  tubes  fitted 
below. 

C,  blow-pipe,  with  issuing  gas-jet.     The  two 
gases  only  mix  at  the  end  of  the  jet,  fol- 
lowing separate  conduits  up  to  this  point, 
one  cylindrical,  the  other  annular,  sur- 
rounding the  first  as  shown  in  the  detail 
section  on  the  right. 

D,  plate  of  magnesia,  which  becomes  incan- 
descent under  the  action  of  the  lighted 
gaseous  mixture. 


arc-electric  light  itself. 
The  first  consisted  in  the  employment  of  a  cylindrical  cage 
of  platinum  wire  brought  to  incandescence  by  the  heat  from 


HISTORY  OF  THE  ELECTRIC  LIGHT.  11 

a  jet  of  hydrogen  gas.  This  system  was  publicly  experi- 
mented with  in  1859,  in  some  streets  of  Narbonne.  The  effect 
was  satisfactory,  but  it  was  far  too  expensive. 

The  other  system,  invented  by  Mr.  Drummond,  was  modi- 
fied by  M.  Tessie  du  Motay,  who  made  several  trials  of  it 
from  1867  to  1872  in  different  localities  in  France,  notably  in 
the  Place  de  ] 'Hotel  de  Ville  and  the  Place  du  Carrousel. 
The  Drummond  system,  still  in  use  for  experiments,  consists 
in  heating  a  pencil  of  lime  by  the  heat  developed  by  the  com- 
bustion of  a  gas-jet  formed  of  two  volumes  of  hydrogen  and 
one  of  oxygen.  M.  Tessie  du  Motay  replaced  the  hydrogen 
by  ordinary  coal-gas,  and  the  lime  by  compressed  magnesia 
(Fig.  8). 

The  same  objections  were  made  to  the  too  great  intensity 
and  too  great  whiteness  of  the  light  that  are  made  to  the  elec- 
tric light  to-day.  Lamps  on  this  system  can  give  a  light  of 
twenty  Carcel  lamps,  by  burning  about  two  hundred  litres 
(seven  cubic  feet)  of  gas  per  hour.  But  the  cost  of  produc- 
tion, and  of  the  separate  gas  mains  and  pipes  for  the  oxygen 
gas,  raise  materially  the  cost  of  this  light. 


CHAPTER  II. 

HISTORY  OF  THE  ELECTRIC  LIGHT. 

IT  would  be  going  too  far  to  trace  the  history  of  the  electric 
light  back  to  the  Greeks  of  the  heroic  epoch,  that  is  to  say, 
to  Thales  of  Miletus,  considered  by  many  savants  as  the  first 
ancestor  of  our  electricians,  because  he  is  supposed  to  have 
known  the  attraction  developed  in  yellow  amber  by  friction. 
But,  without  going  so  far  back,  mention  must  be  made  of  the 
inventor  of  the  first  electric  machine,  in  the  latter  half  of  the 
seventeenth  century,  the  studious  burgomaster  of  Magde- 
burg, Otto  von  Guericke,  to  whom  also  is  due  the  first  air- 
pump. 

We  know  that  Otto  von  Guericke  produced  electricity  by 
rubbing  a  globe  of  sulphur  with  the  hand  (Fig.  9).  He  is  the 
first  who  produced  light  from  this  electricity  ;  this  was  rather 
a  faint  glow,  like  that  of  phosphorus  in  the  air,  for  he  com- 


HISTORY  OF  THE  ELECTRIC  LIGHT.  13 

pares  it  to  the  light  produced  by  rubbing  pieces  of  sugar  to- 
gether in  the  dark.  It  is  a  long  way  from  this  insignificant 
and  fugitive  light  to  the  immense  lights  of  to-day  which  rival 
the  sun.  Yet  the  cause  is  the  same  :  the  whole  question  is  to 
concentrate  it  sufficiently  and  to  properly  regulate  it. 

The  glow  seen  by  Otto  von  Guericke  was  soon  noticed 
more  clearly  by  Dr.  Wall.  He  obtained  electricity  by  rub- 
bing a  stick  of  amber  with  a  linen  cloth,  which  augments  the 
quantities  of  electricity  produced  and  makes  the  phenomena 
more  sensible.  Upon  squeezing  the  amber  tightly  while  rub- 
bing it,  he  heard  a  prodigious  number  of  cracklings,  accom- 
panied by  flashes  of  light.  Rubbing  the  amber  lightly,  the 
luminous  flashes  were  produced  alone,  without  any  noise ; 
finally,  if  the  finger  was  brought  close  to  the  piece  of  amber, 
a  loud  noise  accompanied  by  a  great  flash  of  light  was  pro- 
duced. It  was  the  electric  spark,  perfectly  characteristic, 
though  very  feeble  under  such  circumstances. 

"I  have  no  doubt,"  added  Dr.  Wall,  uthat  by  using  a 
larger  and  longer  piece  of  amber  both  the  noise  and  the  light 
would  be  greatly  increased.  This  light  and  noise  appear  to 
represent  in  a  certain  fashion  thunder  and  lightning." 

This  comparison  would  seem  overdrawn  for  a  spark  which 
seems  to-day  so  very  small.  But  it  is  none  the  less  remark- 
able to  see  the  analogy  between  lightning  and  electricity 
clearly  presented  at  the  commencement  of  electrical  studies, 
nearly  a  century  before  Franklin,  who  thought  himself  ven- 
turesome in  declaring  it,  and  feared  that  he  would  seem 
ridiculous  in  trying  to  prove  it ;  for  it  is  known  that  he  hid 
himself  carefully  from  his  friends  in  making  his  famous  ex- 
periment with  a  kite  made  to  ascend  into  a  thunder-cloud 
(Fig.  10),  the  string  of  which  kite  gave  sparks  of  electricity. 

This  exceeding  correctness  appears  more  remarkable  in 
Dr.  Wall,  because  it  was  joined  in  his  mind  to  the  wildest 
ideas.  After  he  had  most  satisfactorily  demonstrated  that  all 
electrified  bodies  produced  light,  in  the  same  way  as  amber 
and  sulphur,  he  called  this  light  the  cause  of  electricity,  em- 
ployed it  as  an  infallible  means  of  distinguishing  true  from 
false  diamonds ;  affirmed,  moreover,  that  it  only  was  pro- 
duced at  night,  and  that  the  most  favorable  period  was  when 
the  sun  had  gone  eighteen  degrees  below  the  horizon  !  In 
spite  of  the  moonlight,  the  electric  light  was  produced  then 
with  the  same  brightness  as  characterized  it  in  the  most  pro- 


14  HISTORY  OF  ARTIFICIAL  LIGHTING. 

found  darkness — all  which  made  him  bestow  upon  his  fantas- 
tic godchild  the  name  of  noctiluca. 

A  short  time  after  Wall,  an  Englishman,  named  Francis 
Hawksbee,  studied  static  electricity,  following  the  track  of 


FIG.  10. — Franklin  making  the  experiment  with  a  kite,  to  establish  the  identity  of  lightning 

and  electricity. 

Wall,  but  with  less  visionary  ideas.  He  also  considered  the 
electric  light  as  a  phosphorescent  light,  which  he  compared 
to  that  emitted  by  sugar  when  rubbed.  But  he  succeeded  in 
producing  it  in  much  greater  quantity  by  diiferent  means, 


HISTORY  OF  THE  ELECTRIC  LIGHT.  15 

and  notably  by  shaking  mercury  in  a  vessel  of  glass  which  he 
had  previously  exhausted  of  air.  Dominated  by  his  errone- 
ous theories,  he  called  this  electric  light,  produced  by  the 
friction  between  glass  and  mercury,  mercurial  phosphorus. 
On  another  occasion  he  used  melted  wax  to  cover  half  the 
interior  surface  of  a  glass  globe  exhausted  of  air ;  this  he 
moved  about,  applying  his  hand  to  the  upper  surface  to  elec- 
trify it.  He  was  greatly  astonished  to  see  his  hand  appear 
within  and  through  the  wax,  which  in  places  was  over  an 
eighth  of  an  inch  in  thickness. 

"  But  the  greatest  electric  light  which  Hawksbee  ever  pro- 
duced," says  Priestley,  uwas  when  he  inclosed  a  cylinder 
exhausted  of  air  within  another  not  exhausted  and  when  he 
rubbed  the  exterior,  moving  both  cylinders  at  the  same  time. 
He  found  no  difference  in  the  effects  whether  both  moved  to- 
gether or  not.  He  adds  that,  when  the  outer  cylinder  alone 
moved,  the  light  became  quite  strong,  and  extended  itself 
over  the  surface  of  the  inner  vessel.  But  what  most  surprised 
him  was  this  :  After  both  vessels  had  been  moving  for  some 
time,  during  which  he  had  applied  his  hand  to  the  surface  of 
the  exterior  vessel,  if  the  combined  movement  ceased,  there 
was  no  light ;  but,  if  then  he  brought  his  hand  near  the  sur- 
face of  the  exterior  vessel,  flashes  of  light  like  the  aurora  were 
produced  within  the  inner  vessel.  It  would  appear  that  the 
emanations  from  the  exterior  vessel  were  made  to  impinge 
upon  the  inner  vessel  with  more  force  by  the  simple  approach 
of  the  hand." 

All  these  facts,  which  disconcerted  as  well  as  astonished 
the  old  physicists,  are  without  difficulty  explained  to-day,  and 
have  for  us  no  more  than  an  historic  interest.  But  we  see  that 
the  faint  glow  of  Otto  von  Guericke  had  already  made  much 
progress  ;  it  was  destined  to  increase  and  attain  far  greater 
proportions  in  the  eighteenth  century,  and  above  all  to  be 
distributed  by  wires,  an  improvement  destined  to  increase  its 
power  tenfold. 

Under  the  English  physicist  Grey,  electricity  was  studied 
in  an  altogether  new  way.      The  territory  of  chimera  and 
chance  observations  was  abandoned  in  favor  of  the  "more  ra- 
tional course  of  experimental  studies,  which  at  last  took  pos- 
session of  all  the  sciences.     In  172jf  he  proved,  in  a  series  of  I  5| 
experiments  made  in  conjunction  with  flhnlirr .JJjTM^ltai^        *  * 
substances  conducted  the  electric  virtue,  as  it  was  then  called, 


16  HISTORY   OF  ARTIFICIAL  LIGHTING. 

so  that  the  attractive  properties  of  bodies  electrified  by  fric- 
tion could  thus  be  transmitted  to  great  distances.  The  metals 
were  found  particularly  available.  Other  bodies,  on  the  con- 
trary, did  not  enjoy  this  property,  and  did  not  transmit  the 
electric  virtue  ;  this,  for  example,  was  the  case  with  silk. 

Electric  conductivity,  and  in  consequence  the  essentially 
mobile  nature  of  electricity,  was  established  by  these  experi- 
ments. Several  other  discoveries,  only  realized  at  a  later  period 
— such  as  electrization  by  induction — were  foreshadowed  by 
Grey.  Had  he  lived  a  century  earlier,  he  would  probably 
have  affirmed  them  without  waiting  ;  but  the  experimental 
method  prohibited  men  of  science  from  advancing  any  theo- 
ries except  so  far  as  they  were  able  to  prove  the  truth  of  their 
position  to  all  by  tangible  facts. 

After  having  proved  metallic  conductivity,  Grey  observed 
the  escape  of  electricity  from  points,  a  manifestation  which 
constitutes  the  electric  taper,  and  he  showed  that  the  spark  is 
due  to  a  true  movement  of  electricity. 

He  observed,  in  fact,  that  the  spark,  drawn  from  water 
contained  in  a  vessel  about  an  inch  distant,  produced  a  little 
mountain  of  water  of  conical  form.  From  the  summit  of 
this  mountain  of  water  a  light,  perfectly  visible  in  darkness, 
emanated.  Next,  the  mountain  shrank  within  itself,  and  fell 
back  into  the  general  mass  of  liquid,  to  which  a  trembling  and 
undulatory  movement  was  imparted.  Grey  even  succeeded 
in  discovering  in  this  experiment  still  better  evidence  of  me- 
chanical transportation  ;  he  showed  that  the  little  liquid  par- 
ticles flew  upward  with  the  light  from  the  summit  of  the 
mountain,  and  that  there  was  thus  formed,  at  the  top  of  the 
cone,  a  very  minute  thread  of  water  emitting  a  fine  spray  or 
mist,  so  delicate  that  it  could  hardly  be  discerned. 

In  consequence  of  his  experiments,  Grey  declared  that  he 
could  by  means  of  electricity  make  cold  water  boil,  and  pro- 
duce from  it  a  flame  and  an  explosion.  The  great  future  of 
this  flame  appeared  very  clearly  to  him,  for  he  says,  "Al- 
though these  effects  have  never  been  hitherto  produced  except 
on  a  very  small  scale,  it  is  probable  that  with  time  a  way  will 
be  found  to  accumulate  a  greater  quantity  of  electric  fire,  and 
consequently  to  increase  the  potency  of  this  force,  which,  from 
several  of  these  experiments  (si  parvas  de  magnis  componere 
licet),  would  seem  to  be  of  the  same  nature  as  that  of  thunder 
and  lightning." 


HISTORY  OF  THE   ELECTRIC  LIGHT. 


17 


We  now  have  reached  the  end  of  the  first  quarter  of  the 
eighteenth  century,  about  1727.  It  is  the  idea  of  Wall  which 
reappeared  twenty  years  later,  but  emanated  from  the  lips  of 
a  man  of  higher  authority,  trained  in  the  severe  school  of  ex- 
perience, and  who  did  not  trust  to  the  chimeras  of  the  imagi- 
nation. 

All  this  while  electrical  studies  were  extending ;  they 
became  to  a  certain  extent  the  fashion  ;  the  general  pub- 
lic became  interested  in  them,  and  France,  supreme  arbiter 
of  opinions  as  well  as  of 
elegance  in  the  eighteenth 
century,  began  to  be  occu- 
pied with  them.  A  member 
of  the  Academy  of  Sciences 
at  Paris,  Du  Fay,  superin- 
tendent of  the  Jardin  du 
Koi  (to-day  the  Jardin  des 
Plantes),  repeated  Grey's 
experiments,  and  made  new 
ones.  It  was  he  who  first 
produced  a  spark  from  a 
living  body. 

Every  one  knows  to-day 
the  experiment,  which  is  re- 
produced in  the  course  of 
physics,  by  placing  a  child 
on  an  insulating  stool,  and 
making  communication  be- 
tween it  and  the  electric 
machine.  In  itself,  the  ex- 
periment does  not  at  all 
astonish  us.  But  it  then 
produced  an  extraordinary 
sensation,  and  attracted  ev- 
ery one  to  the  new  science. 
The  effects  were  varied  in 

numberless  ways,  and  they  did  not  fail  to  exaggerate  them 
greatly  in  conversations,  or  in  the  periodical  literature  of  the 
subject  then  beginning  to  appear  (Fig.  11). 

The  monks  even  joined  the  popular  movement :  a  Scotch 
Benedictine,  the  reverend  Father  Gordon,  increased  the  force 
of  the  spark  until  it  killed  little  birds,  and  made  a  man  trem- 


FIG.  11. — Experiment  of  electrifying  a  woman, 
from  an  engraving  of  the  eighteenth  century. 


18  HISTORY   OF  ARTIFICIAL  LIGHTING. 

S 

ble  from  head  to  foot  with  its  peculiar  agitation.  A  professor 
of  dead  languages  at  the  University  of  Leipsic,  abandoning 
the  ancient  classic  humanities  for  the  study  of  the  new  sci- 
ence, increased  still  further  the  force  of  electric  machines  by 
increasing  the  rapidity  of  rotation  of  the  globes  or  cylinders 
which  composed  them.  He  reached  as  many  as  six  hundred 
and  eighty  turns  a  minute,  and  obtained  sparks  which  burned 
the  skin  like  a  caustic,  and  made  the  blood  in  the  veins  gush 
out,  and  accomplished,  according  to  the  stories  of  the  contem- 
porary savants,  many  other  horrible  things. 

In  1744  a  savant  of  Berlin,  named*  Ludolf,  ignited  ether 
with  the  spark  ;  and,  later,  another  scientist,  Boze,  performed 
the  most  paradoxical  experiment  of  all,  by  igniting  alcohol 
and  spirituous  liquors  by  a  jet  of  water  which  served  as  con- 
ductor for  the  electricity. 

In  1746,  in  a  memoir  read  before  the  Royal  Society  of  Lon- 
don on  the  6th  of  February,  Dr.  Watson  demonstrated  that 
the  electric  sparks  appeared  of  different  colors  according  to 
the  nature  of  the  substance  from  which  they  emanated. 
Bodies  with  roughened  surfaces,  such  as  rusty  iron  or  oxi- 
dized copper,  gave  redder  sparks  than  bodies  with  clean  sur- 
faces. 

But  it  was  long  before  the  full  signification  of  this  fact  was 
known,  which  should  have  furnished  the  explanation  of  the 
true  nature  of  the  electric  spark.  The  spark,  in  fact,  is  in- 
debted for  its  brilliancy  to  the  particles  which  it  detaches 
from  the  more  or  less  volatilized  conductors,  and  carries  off 
with  itself  ;  its  color,  therefore,  should  vary  according  to  the 
nature  of  these  particles — that  is  to  say,  of  the  conductors 
whence  it  emanates.  Watson  approached  very  closely  the 
true  explanation,  simple  as  we  know  it  to  be,  yet  tried  to  find 
a  complicated  cause  for  the  phenomenon  in  the  difference  of 
reflection  of  light  according  to  the  variable  nature  of  the  sub- 
stances reflecting  it. 

Finally,  it  was  this  savant  who  first  produced  a  real  electric 
light.  By  uniting  in  action  four  of  the  globes,  which  fur- 
nished him,  by  their  rotation,  with  electricity,  he  produced 
genuine  jets  of  flame,  which  gave  almost  a  continuous  light, 
because  of  their  size  and  rapid  succession.  The  experiment 
was  naturally  conducted  in  a  dark  room,  and  light  enough 
was  produced  to  show  distinctly  the  features  of  the  persons 
present. 


HISTORY  OF  THE  ELECTRIC  LIGHT.  19 

During  this  same  year  (1746)  Muschenbroek  and  Cuneus 
discovered  at  Leyden,  in  Holland,  the  principles  of  electrical 
condensation.  They  accumulated  in  the  famous  Leyden- jars 
quantities  of  electricity  which  were  enormous  for  the  epoch, 
and  which  enabled  them  to  produce  electric  phenomena  of  an 


FIG.  12. — The  Abbe"  Nollet  giving  a  lesson  in  electricity. 

altogether  new  intensity  ;  for  example,  to  pass  an  electric  dis- 
charge through  the  bodies  of  all  the  soldiers  of  a  regiment. 
But  it  is  only  in  our  century  that  the  means  of  rendering  the 
light  more  intense,  and  above  all  more  continuous,  was  sought 
for  in  this  direction. 


20 


HISTORY   OF  ARTIFICIAL  LIGHTING. 


During  the  second  half  of  the  eighteenth  century  the 
labors  of  the  following  electricians — the  Abbe  Nollet,  Frank- 
lin, Father  Beccaria,  Canton,  Dr.  Desaugiers,  and  of  many 
others — did  not  furnish  a  single  new  element  to  the  electric 
light.  But  the  knowledge  of  electricity  continued  to  de- 
velop, and  apparatus  was  invented  for  measuring  it  (Fig.  13). 
It  was  only  in  1800  that  the  decisive  fact  appeared  which 
opened  a  way,  entirely  new,  by  which  the  electric  light  could 
be  produced,  not  as  a  mere  curiosity  of  the  laboratory,  as  in 
Watson's  experiment,  but  in  the  state  of  practical  and  every- 


Fio.  13. — Electrometer,  after  the  design  in  the  Encyclopaedia. 

day  application,  as  we  now  witness  it.  This  achievement  was 
the  invention  of  the  pile  or  battery  by  Volta — the  discovery, 
in  fact,  of  electricity  in  the  dynamic  state,  or  state  of  currents, 
which  we  shall  endeavor  to  illustrate  and  explain  in  its  move- 
ment and  action  in  the  next  chapter. 

The  wonderful  invention  of  Volta,  inspired  by  the  well- 
known  experiment  of  Galvani,  gave  electrical  studies  at  once 
a  new  direction.  The  ways  trodden  for  three  quarters  of  a 
century  (since  the  experiments  of  Grey)  were  deserted,  and 
the  new  territory,  whose  bonds  of  union  with  the  old  were 


HISTORY  OF  THE  ELECTRIC  LIGHT.  21 

not  as  yet  understood,  was  eagerly  explored.  A  complete  re- 
vision of  the  old  experiments  had  to  be  made,  for  the  lumin- 
ous effects  as  well  as  for  the  others.  It  was  perhaps  in  that 
direction  that  the  most  striking  results  were  attained. 

Thirteen  years  after  the  discovery  of  Yolta,  in  1813,  Sir 
Humphry  Davy,  bringing  near  together  the  terminals  or 
electrodes  of  a  powerful  battery,  caused  a  jet  of  flame  to 
play  between  these  electrodes,  which  was  not  momentary  like 
the  electric  spark,  but  was  continuous.  It  was  the  voltaic 
arc,  observed  for  the  first  time  in  London  in  the  laboratory  of 
the  Royal  Institution  of  Great  Britain,  which,  since  then,  has 
been  the  theatre  for  the  production  of  so  many  beautiful  re- 
searches in  magnetism  and  electricity,  particularly  of  those  of 
Faraday. 

The  battery  used  by  Sir  Humphry  Davy  had  as  many  as 
two  thousand  elements,  and  the  active  surface  of  all  these 
elements  came  to  a  sum  total  of  eighty  square  metres.  Over- 
whelming as  the  production  of  light  was,  it  could  not  cause 
the  enormous  apparatus  to  be  ignored,  more  costly  even  than 
cumbrous,  and  it  is  hard  to  dream  for  a  moment  of  the  intro- 
duction into  ordinary  life  of  so  expensive  a  light. 

Nevertheless,  the  study  of  the  electric  light  was  prose- 
cuted. Sir  Humphry  Davy  had  placed  at  the  extremities  of 
his  electrodes  two  carbons,  which  became  incandescent  by  the 
passage  of  the  current,  and  which  furnished  the  necessary 
elements  to  render  the  flame  brilliant.  These  carbons  could 
be  drawn  ten  centimetres  apart  without  extinguishing  the 
wonderful  light  which  had  been  produced,  and  without  even 
weakening  it.  How  did  the  electricity  pass  \  and  would  this 
open  space  be  an  obstacle  to  its  passage  ?  A  crowd  of  savants 
devoted  themselves  to  these  questions  in  England,  in  France, 
in  Switzerland,  in  Germany,  in  Italy.  Sir  Humphry  Davy 
showed  that  the  electric  light  sprang  through  a  vacuum  as 
through  air,  but  with  more  difficulty,  and  the  difficulty  grew 
with  the  increased  vacuum.  Thus,  in  the  imperfect  vacuum 
of  the  air-pump,  it  passed  over  six  times  as  great  an  interval 
as  that  which  arrested  it  in  the  more  perfect  Torrecellian 
vacuum.  But  Davy  persisted  in  believing,  in  spite  of  the  ob- 
jections of  Father  Beccaria,  that  the  electric  light  could  be 
propagated  in  an  absolute  vacuum,  if  such  could  be  produced. 

Much  later,  in  1850,  when  the  electric  light  began  to  enter, 
if  not  into  the  domain  of  practice,  at  least  into  the  laborato- 


22  HISTORY  OF  ARTIFICIAL   LIGHTING. 

ries,  Masson,  Professor  of  Physics  in  the  Ecole  Centrale  des 
Arts  et  Manufactures  in  Paris,  repeated  the  experiments  of 
Sir  Humphry  Davy.  He  concluded  that  electricity  could  pro- 
duce no  current  in  an  absolute  vacuum,  and,  in  consequence, 
no  voltaic  arc.  In  fine,  the  light  produced  by  this  arc  ap- 
peared to  have  the  same  cause  as  that  of  the  electric  spark  : 
it  is  due  to  the  transport  by  electricity  of  the  incandescent 
particles  of  the  electrodes.  These  results  are  the  more  readily 
admitted  to-day,  as  they  have  been  confirmed  by  the  researches 
of  Matteucci,  coming  soon  after  those  of  Masson. 

When  it  came  to  the  practical  applications,  a  host  of  diffi- 
culties were  encountered.  Nevertheless,  in  1841  and  1844, 
two  French  savants,  MM.  Deleuil  and  Archereau,  had  con- 
ducted in  Paris,  on  the  Conti  dock  and  Place  de  la  Concorde, 
public  experiments  which  excited  the  astonishment  and  admi- 
ration of  all.  They  developed  the  electric  arc  in  a  closed 
vessel,  exhausted  of  air  to  retard  the  combustion  of  the  car- 
bons. They  already  hoped  to  increase  the  power  of  their 
apparatus,  so  as  to  create  little  suns  for  the  use  of  cities  not 
favored  by  the  real  one.  This  idea  dates  still  further  back, 
for  a  professor  of  the  University  of  Halle,  named  Meinake,  had 
already  made  the  same  suggestion  in  1821  (Colburn,  "  Prac- 
tical Economy").  But,  in  1844,  as  in  1821,  this  was  but  a 
dream  without  serious  foundation,  because  everything  was 
wanting  that  would  be  required  to  realize  it  even  in  part. 
Again,  batteries  strong  enough  to  illuminate  such  areas  of 
lighting  could  not  be  constructed  at  any  price.  Finally,  car- 
bons capable  of  giving  a  good  light  for  a  sufficient  period  were 
unknown. 

As  the  carbons  burned  up  during  the  passage  of  the  elec- 
tric current,  and  grew  shorter,  some  means  had  to  be  found  to 
bring  them  together — either  good  regulators  or  other  means. 
This  was  the  programme  thirty  years  ago.  We  can  say  that 
it  has  been  carried  out  to-day,  and  that  every  problem  in  it 
has  received  generally  several  solutions. 

The  first  really  practical  application — that  is  to  say,  paid 
for — was  in  1846,  for  a  special  object.  The  sun  was  to  appear 
during  the  opera  of  "  The  Prophet."  Recourse  was  had  to 
electricity,  and  such  was  its  success  that,  under  the  auspices 
of  M.  Dubosq,  a  regular  service  for  its  administration  was  or- 
ganized. 

At  the  end  of  the  succeeding  year  (1847),  W.  E.  Staite  pub- 


HISTORY  OF  THE  ELECTRIC   LIGHT.  23 

licly  experimented  with,  it  in  England,  in  the  large  hall  of  a 
hotel  of  Sunderland.  It  was  probably  the  first  trial  of  ordi- 
nary lighting  by  electricity,  because  no  account  has  reached 
us  of  a  reduction  to  practice  of  the  earlier  patents  of  De  Mo- 
leyns  (August  21, 1841),  Thomas  Wright  (March  10, 1845),  and 
E.  A.  King  (November  4,  1845),  all  taken  out  in  London. 
This  lighting  of  Sunderland  seems  to  have  lasted  some  time, 
and  the  great  journal  of  London,  the  "Times,"  became  quite 
enthusiastic  over  it.  Its  power,  it  said,  was  immense  ;  it  re- 
sembled the  sun,  or  the  light  of  day,  and  made  candles  appear 
as  obscure  as  they  do  by  daylight  (November  2,  1848). 

During  four  years  the  inventor  multiplied  his  experiments 
in  a  certain  number  of  cities  of  England,  and  in  1852  the  di- 
rectors of  the  Liverpool  docks  placed  a  large  apparatus  on 
his  system  on  top  of  a  tower  built  expressly  for  the  purpose. 
But  in  this  year  Staite  died,  and  his  idea  was  consigned  with 
him  to  the  tomb. 

All  this  did  not  pass  unremarked  in  France,  and  it  had 
even  been  spoken  of  in  the  Academy  of  Sciences  in  Paris  in 
the  beginning  of  the  year  1849.  Two  Lyonnese,  MM.  J.  Lacas- 
sagne  and  Rudolphe  Thiers,  took  up  the  question  soon  after 
the  death  of  Staite.  They  patented,  in  the  beginning  of  the 
year  1855,  a  new  form  of  regulator,  in  which  the  lower  car- 
bon rested  on  a  column  of  mercury  which  raised  it  up,  in 
proportion  to  the  rate  of  its  combustion,  by  aid  of  a  special 
mechanism. 

The  first  public  experiments  took  place  at  Lyons,  in  the 
month  of  June,  1855,  on  the  quai  des  Celestins,  and  the  jour- 
nals of  the  period  show  no  less  enthusiasm  than  was  shown  by 
the  "  Times,- '  six  years  before,  over  the  system  of  Staite.  The 
whole  quay  was  flooded,  they  say,  with  refulgent  rays,  by 
v/hich  one  could  read  at  a  distance  of  four  hundred  and  fifty 
metres  from  the  light,  and  the  very  birds,  believing  day  had 
come,  quitted  their  nests  under  the  eaves,  to  fly  about  in  the 
rays  of  the  new  sun  ("  Salut  Public  "). 

The  following  month  the  experiments  were  repeated  at 
Paris,  in  the  chateau  Beaujon,  the  home  of  the  famous  ma- 
rine painter,  Theodore  Gudin.  The  accounts  given  us  are  no 
less  enthusiastic  ;  they  tell  us  that  the  ladies  had  to  open  their 
parasols  to  protect  themselves  from  the  ardors  of  the  mysteri- 
ous star  ("  Gazette  de  France,"  July  5,  1855).  They  tried  to 
interest  the  emperor  in  so  marvelous  an  invention,  and  for  this 


24:  HISTORY  OF  ARTIFICIAL  LIGHTING. 

end  organized  in  the  month  of  October,  1856,  a  grand  demon- 
stration from  the  summit  of  the  Arc  de  Triomphe  de  1'Etoile. 
The  avenue  des  Champs  Elysees  was  thus  illuminated  for  a 
space  of  four  hours. 

This  year  also  saw  experiments  frequently  repeated  in 
Paris  and  Lyons,  notably  in  the  Alcazar,  in  the  Winter  Gar- 
den, in  the  Observatory  of  Fourvieres,  etc.  At  the  beginning 
of  1857,  MM.  Lacassagne  and  R.  Thiers  tried  to  light  perma- 
nently the  Rue  Imperiale  in  Lyons,  with  only  two  centers  of 
illumination ;  and  in  the  month  of  March  experiments  were 
conducted  in  Toulon,  in  the  interest  of  the  light-house  service, 
for  the  illumination  of  the  harbor. 

Little  by  little  the  subject  fell  into  oblivion,  and  not  much 
was  again  heard  of  it  until  1860.  Nevertheless,  during  this 
epoch,  there  were  several  electric  illuminations  on  a  large 
scale  ;  but  they  were  executed  with  the  regulator  of  M.  Ser- 
rin,  invented  in  1859.  Particularly  the  lighting  of  the  tile- 
factories  of  Angers  in  1863  must  be  cited,  and,  above  all,  the 
lighting  of  the  railroad  excavations  of  the  Northern  Spanish 
Railroad  when  crossing  Gfaudarrama,  which  lasted  ten  thou- 
sand hours  ;  then  the  lighting  of  the  work  of  demolishing  la 
Samaritaine,  and  of  various  public  fetes. 

The  principal  obstacle  was  found  in  the  insufficiency  of 
the  means  for  producing  electricity.  The  magneto-electric 
machine  of  Nollet,  simplified  by  Van  Malderen,  was  destined 
to  do  away  with  this  trouble.  This  machine,  known  in  France 
under  the  name  of  the  Societe  T  Alliance,  was  used  as  early  as 
1863  to  light  by  electricity  the  large  light-house  at  Havre,  soon 
after  that  of  Odessa,  and  several  others.  In  1866  a  new  order 
of  applications  for  it  appeared,  the  electric  lighting  of  vessels, 
introduced  for  the  first  time  on  the  yacht  of  Prince  Napoleon, 
the  Prince  Jerome,  which  could  thus  enter  at  night,  and  with- 
out a  pilot,  the  harbors  of  Gibraltar,  Malta,  Constantinople, 
and  Toulon.  The  trial  was  repeated  the  same  year  upon  one 
of  the  large  transatlantic  steamers,  the  Saint-Laurent. 

Finally,  the  invention  of  the  dynamo-electric  machine  of 
Gramme  in  1870  placed  at  the  disposal  of  engineers  as  power- 
ful a  source  of  electricity  as  they  could  wish  for;  and  six  years 
later,  in  1876,  the  Jablochkoff  candle  gave  them  a  burner  so 
simple  in  construction  that  it  was  at  once  accepted  in  every- 
day practice.  The  first  great  application  was  the  lighting  of 
the  Avenue  de  POpera,  decreed  by  the  Municipal  Council  of 


26  HISTORY  OF   ARTIFICIAL  LIGHTING. 

Paris  on  the  occasion  of  the  Universal  Exposition  of  1878,  and 
which  has  been  maintained  to  the  present  day  (Fig.  14). 

Here  the  history  of  the  origin  of  the  electric  light  ends. 
It  passes  now  from  the  stage  of  experiment  to  that  of  indus- 
trial applications,  where  it  had  rarely  made  its  appearance  in 
our  country  (France)  even  after  1870. 


BOOK    II. 
THE    VOLTAIC    ARC. 


CHAPTER  I. 

HOW  THE  ELECTRIC  LIGHT  IS  PRODUCED. 

AT  this  period  in  our  study  and  comparison  of  the  differ- 
ent systems  of  electric  lighting,  which  have  multiplied  greatly 
in  the  last  five  years,  it  is  necessary  to  examine  the  conditions 
under  which  the  electric  light  is  produced,  to  study  its  nature, 
and  ascertain  the  different  means  offered  by  scientific  theories 
for  obtaining  it. 

We  are  entirely  ignorant  of  the  nature  of  electricity,  and 
we  can  not  even  directly  recognize  it  as  we  do  light  and  heat ; 
we  only  know  it  by  its  luminous,  calorific,  chemical,  or  me- 
chanical effects.  Yet,  though  electricity  does  not  fall  under 
any  one  of  our  five  senses,  we  have  a  sort  of  vague  sensation 
of  it,  as,  for  example,  when  the  air  is  charged  with  electricity 
on  the  approach  of  a  thunder-storm.  It  then  produces  in  us 
a  particular  nervous  condition,  before  the  storm  will  have 
manifested  itself  by  any  calorific,  mechanical,  or  luminous 
effects,  and  this  particular  nervous  condition  evidently  corre- 
sponds to  the  electric  state  of  the  atmosphere.  But  all  this 
is  limited  to  a  vague  sensation,  which  does  not  concentrate 
itself  in  any  special  organ,  as  the  organs  of  the  five  senses, 
and  thus  can  not  become  a  distinctly  marked  perception. 

On  the  other  hand,  there  is  no  doubt  that  electricity  is  not 
the  only  one  of  the  properties  of  matter  which  partly  evades 
our  perceptions.  We  may  reasonably  suspect  that  many 
others  are  entirely  unknown  to  us,  even  by  their  effects,  be- 
cause these  effects  are  not  among  those  which  are  perceived 
by  the  five  senses. 

Long  ago  philosophers  remarked  that  our  knowledge  of 


28  THE  VOLTAIC  ARC. 

nature  was  limited  by  the  number  of  our  senses,  and  would 
probably  extend  itself  if  these  were  increased  or  even  per- 
fected. Nothing,  indeed,  authorizes  us  to  believe  that  the 
properties  of  nature  are  limited  to  those  which  aifect  the 
senses  of  man.  Electricity  furnishes  a  good  example  of  a 
material  property  which  we  never  knew  directly,  and  whose 
existence  is  still  perfectly  certain,  since  we  have  for  a  long 
time  studied  it  in  its  manifestations,  and  have  succeeded  in 

I  thoroughly  mastering  it. 
Physicists  who  live  on  intimate  terms  with  this  electric 
agent  have  not  succeeded  any  better  than  the  ordinary  ob- 
servers in  penetrating  into  the  inner  nature  of  this  mysterious 
being,  which,  nevertheless,  they  control  and  direct  at  pleas- 
ure. But,  to  facilitate  their  explanations  of  it,  they  represent 
it  as  an  invisible  fluid,  many  million  times  lighter  than  air, 
and  whose  different  forms  of  movement  produce  electricity, 
heat,  and  light.*  Some  savants  still  admit  two  electric 
fluids — not,  however,  deceiving  themselves  into  believing  in 
the  objective  reality  of  their  theory,  whose  end  is  only  to 
facilitate  the  exposition  of  facts. 

Electricity,  then,  is,  by  hypothesis,  a  sort  of  fluid,  formed 
of  imponderable  molecules,  which  travels  through  material 
bodies — more  or  less  easily,  according  to  the  nature  of  these 
bodies,  that  is  to  say,  according  to  their  conductivity  for  elec- 
tricity— and  which  accumulates  on  their  surfaces.  In*  any 
given  body  completely  removed  from  exterior  influences,  the 
electric  molecules,  left  to  themselves,  would  evidently  seek 
some  order  in  which  they  would  not  further  tend  to  change — 
this  is  what  is  called  a  state  of  equilibrium,  and  then  we  have 
to  deal  with  electricity  in  repose,  or  in  the  static  condition. 

Let  us  next  suppose  that,  by  the  action  of  an  exterior 

,  cause,  this  equilibrium  is  destroyed  at  some  particular  point ; 

for  example,  that  the  density  of  the  molecules  diminishes  at 

*  Some  physicists  may  think  that  our  assertions  overstep  a  little  the  limits 
of  actual  experiment,  and  that  we  give  too  restricted  a  form  to  ideas,  which  in 
actual  science  have  not  such  exact  precision ;  for,  if  the  theory  of  single-fluid 
electricity  has  no  opponents  left,  the  identity  of  this  fluid  with  the  luminiferous 
ether  is  not  formally  established  hy  any  direct  experiments ;  but,  as  soon  as  the 
phenomena  of  electricity  are  explained  by  the  single-fluid  theory,  the  principles 
of  scientific  method  force  us,  if  nothing  opposes,  to  confound  it  with  the  fluid 
that  is  the  cause  of  luminous  phenomena.  In  short,  we  have  no  right  to  multi- 
ply hypotheses  without  necessity. 


HOW  THE    ELECTRIC  LIGHT  IS  PRODUCED.  29 

this  point.  The  effect  is  the  same  as  may  be  produced  in  a 
gas,  such  as  air,  for  example :  the  electric  molecules  of  the 
surrounding  space  flow  toward  the  point  of  rarefaction  to 
re-establish  the  equilibrium ;  there  will  be,  it  may  be  said, 
a  sort  of  electric  wind,  provided,  be  it  understood,  that  the 
electric  molecules  can  move  in  the  body  in  which  these  actions 
are  taking  place  ;  in  other  words,  provided  the  body  is  a  good 
conductor.  The  same  thing  in  inverse  effect  will  be  produced 
if  the  electric  density  be  augmented  at  any  point :  an  electric 
wind  will  be  produced  directed  away  from  this  overburdened 
point  toward  the  parts  containing  fewer  molecules. 

It  is  this  species  of  electrical  wind  that  is  called  a  current. 
Electricity  is  no  more  in  the  static  condition  ;  it  is  in  motion  ; 
it  is  dynamic  electricity,  the  electricity  of  Volta,  or  of  batter- 
ies, the  variety  that  furnishes  almost  all  the  applications  of 
electricity,  and  especially  the  electric  light. 

The  function  of  the  current  is  only  to  re-establish  the 
overturned  electrical  equilibrium  ;  it  should  then  disappear  as 
soon  as  this  equilibrium  is  re-established.  Consequently,  if 
the  cause  which  has  destroyed  the  equilibrium  is  temporary 
in  its  action,  the  current  will  last  only  a  short  time  ;  it  will  be 
a  simple  discharge.  But  it  will  be  altogether  different  if  this 
cause  is  permanent,  or  at  least  greatly  prolonged — if,  for  ex- 
ample, the  excess  of  the  density  of  the  electric  molecules  at 
a  given  point  is  maintained,  in  spite  of  the  escape  of  this 
excess  to  neighboring  points.  Then  a  continuous  current  is 
formed,  a  true  current,  quite  comparable  to  a  brook,  which 
will  have  its  origin  in  a  place  where  density  is  always  in  ex- 
cess, as  we  may  boldly  say,  in  the  electric  spring,  for  thence 
it  is  that  the  current  of  electric  molecules  supports  itself. 

Running  water,  to  form  a  stream  or  river,  should  concen- 
trate itself  in  a  bed  which  fixes  its  direction  and  makes  its 
force  sensible.  It  is  the  same  for  the  electric  current,  which 
should  follow  a  conductor,  drawn  out  in  form  like  a  wire,  to 
produce  visible  effects.  As  its  end  and  result  is  to  re-establish 
the  equilibrium  destroyed  throughout  the  extent  of  the  con- 
ducting system,  the  two  free  extremities  must  be  united  so  as 
to  form  a  complete  circuit  of  any  form — for  it  will  often  be 
made  of  a  perfectly  flexible  wire — but  which  can  be  repre- 
sented to  our  minds  as  a  circle  to  facilitate  our  conception  of 
the  phenomenon. 

Here  the  analogy  with  the  stream  would  seem  defective, 


30  THE   VOLTAIC  ARC. 

for  rivers  do  not,  at  first  sight,  seem  to  form  closed  circuits ; 
they  fall  into  the  seas  or  oceans,  which  form  for  them  indefi- 
nitely large  reservoirs.  Nevertheless,  large  as  they  are,  these 
reservoirs  would  be  overflowing  if  the  heat  of  the  sun  did  not 
vaporize  the  water  of  the  sea,  and  pump  it  up  under  the  form 
of  clouds  which  finally  dissolve  in  rain,  which  rain  nourishes 
the  springs  of  the  rivers  or  brooks.  It  is  thus  that  the  circuit 
closes,  as  perfectly,  it  will  be  seen,  as  in  the  case  of  an  elec- 
tric current ;  and  thus  also  the  current  would  cease  if  the  sea 
did  not  vaporize  so  as  to  keep  a  place  free  for  the  discharge 
of  the  waters  of  the  rivers  ;  for  in  this  case  the  springs  would 
dry  up  for  want  of  rain. 

If  the  circuit  is  not  closed — that  is  to  say,  if  it  is  incom- 
plete— the  current  reaching  the  end  most  remote  from  the 
spring  would  find  no  means  of  discharge  ;  it  would  practically 
be  dammed  up,  and  the  electric  molecules  would  accumulate 
at  this  extremity.  The  power  which  they  tend  to  exert  in 
escaping  is  called  their  potential. 

As  often  as  the  equilibrium  of  electric  molecules  is  de- 
stroyed in  a  conducting  body,  or,  to  express  it  differently, 
when  a  difference  of  potential  is  established  between  two 
points  of  a  circuit,  an  electric  current  is  necessarily  produced. 
Whatever  the  force  may  be  that  tends  to  destroy  this  equilib- 
rium is  the  true  cause  of  the  current ;  it  is  called,  in  a  general 
way,  electro-motive  force,  but  its  particular  nature  may  vary 
greatly. 

The  current  has  two  distinct  properties,  quantity  and 
tension — properties  which  play  very  different  roles  in  different 
electrical  apparatus,  and  which  must  be  taken  into  strict  ac- 
count in  order  to  understand  the  phenomena  which  accom- 
pany the  production  of  the  electric  light. 

The  electric  molecules  which  are  put  into  motion  by  the 
electro-motive  force  encounter  a  certain  amount  of  resistance  ; 
to  overcome  it  this  same  electromotive  force  must  expend  a 
certain  part  of  its  energy  in  giving  these  molecules  a  sufficient 
impulse.  It  is  the  state  in  which  they  find  themselves  when 
obeying  this  impulse  which  is  called  their  tension. 

It  follows  that  the  quantity  of  molecules  put  in  motion  by 
the  same  electro-motive  force  increases  or  diminishes  inversely 
as  the  resistance  which  opposes  their  motion,  or,  what  is  the 
same  thing,  to  the  tension  which  they  may  possess. 

The  final  result— that  is  to  say,  the  quantity  of  molecules 


HOW   THE  ELECTRIC  LIGHT  IS  PRODUCED.  31 

in  movement  with  a  determined  tension — is  called  the  intensity 
of  the  current,  an  intensity  which  Ohm  has  represented  by  the 
relation  between  the  electro-motive  force  and  the  resistance, 
because,  in  effect,  the  intensity  of  a  current  does  not  only  de- 
pend on  the  energy  of  the  electro-motive  force,  but  it  depends 
also  on  the  resistance  of  the  circuit  in  which  this  current  is 
developed. 

In  all  cases  a  certain  minimum  of  tension  is  required  to 
establish  the  current.  This  minimum  depends  upon  the  ob- 
stacles which  the  current  has  to  overcome.  If  the  circuit  was 
completely  closed  and  formed  of  a  substance  of  perfect  con- 
ductivity, offering  no  resistance  to  the  passage  of  the  electric 
molecules,  these  obstacles  would  not  exist,  and  an  infinitely 
small  tension  would  suffice.  But  this  case  is  rarely  realized. 
In  fact,  no  substance  is  a  perfect  conductor.  The  imperfec- 
tion of  this  conductivity  constitutes  the  resistance  to  the  pas- 
sage of  the  current,  which  thus  is  the  inverse  of  the  conduc- 
tivity. It  may  be  compared  to  the  friction  which  the  stream, 
or  any  liquid  flowing  in  a  tube  or  aqueduct,  encounters. 
This  resistance  diminishes  the  living  force  of  the  current,  as 
the  friction  diminishes  the  force  of  the  water;  but  just  as 
there  are  surfaces  more  or  less  favorable  to  the  flowing  of 
water,  there  are  materials  more  resisting  than  others  to  the 
passage  of  electrical  molecules. 

To  conceive  of  the  production  of  heat  and  light  by  the 
passage  of  electric  currents  in  conducting  bodies,  it  is  neces- 
sary to  remember  that  all  bodies  of  this  nature  are  composed 
of  molecules  animated  by  a  continual  motion  of  vibration ; 
that  their  temperature  increases  or  decreases  in  inverse  ratio 
with  the  amplitude  and  duration  of  these  vibrations  ;  finally, 
that  these  vibrations  of  the  molecules  of  matter  are  repro- 
duced by  those  of  the  ether  which  surrounds  them,  and  by 
whose  agency  they  produce  their  effects  upon  us. 

The  molecules  which  we  call  electric  molecules  are  no 
other  than  the  molecules  of  ether,  impressed  with  a  particular 
movement,  and  moving  through  bodies  whose  molecules  bear 
such  a  relation  to  them  that  the  first  set  of  molecules  pass 
between  the  second  set  without  much  loss  of  their  own  move- 
ment. 

Electric  conductivity,  calorific  conductivity,  and  trans- 
parency, are  states  of  matter  corresponding  to  those  move- 
ments of  ether  which  we  call  electricity,  heat,  and  light. 


32  THE  VOLTAIC  ARC. 

If  two  conductors  made  of  the  same  material  be  compared, 
we  should  naturally  expect  the  electric  molecules  to  move 
easier  in  the  larger,  just  as  water  would  run  easier  in  a  tube 
of  large  than  in  one  of  small  caliber.  Resistance  then  dimin- 
ishes as  the  conductor  is  enlarged,  and  Ohm  has  shown  that 
it  is  inversely  proportional  to  the  cross-section  of  the  con- 
ductor—that is  to  say,  to  the  surface  of  the  cut  obtained  in 
dividing  it  perpendicularly  to  its  length.  Following  this 
out,  if  the  conductor  diminishes  the  resistance  increases,  the 
molecules  squeeze  closer,  as  it  were,  so  as  to  pass  without 
retarding  their  companions  ;  as  they  pass  through  it  they  rub 
against  the  molecules  of  the  conductor,  whose  vibrations  thus 
become  more  rapid  ;  the  metallic  wire  gets  hot,  which  further 
diminishes  its  conductivity ;  and,  finally,  it  becomes  red-hot. 
If  the  current  is  intense  and  the  resistance  considerable,  the 
temperature  rapidly  rises,  and  the  conductor  becomes  incan- 
descent. Here  we  have  reached  the  electric  light. 

Then,  if  the  current  of  electricity  meets  no  resistance,  it 
passes  through  the  molecules  of  the  conductor  without  dis- 
turbing them,  or  the  disturbance  is  so  slight  that  the  heat 
resulting  is  quite  balanced  by  the  cooling  due  to  radiation ; 
but,  if  at  any  point  of  the  circuit  any  particular  object  pre- 
sents itself  which  prevents  the  current  from  going  freely  on 
its  way,  since  it  is  necessary  that  the  same  number  of  mole- 
cules traverse  in  the  same  time  all  points  of  the  circuit,  a  dis- 
turbance is  produced  at  the  point  where  the  obstacle  exists : 
the  electric  molecules  yield  up  a  part  of  their  electric  force 
to  the  molecules  of  the  conductor,  and  it  is  the  augmentation 
of  movement  impressed  on  these  last  which  creates  the  heat, 
and  in  consequence  the  light. 

This  particular  obstacle  can  be  created  in  several  ways,  to 
each  of  which  one  variety  of  the  electric  light  corresponds. 

It  may  happen  that  the  circuit,  properly  so  called,  may 
be  interrupted,  so  that  the  current  has  to  pass  through  the 
air  by  an  intermediary  gaseous  conductor  ;  there  is  then  pro- 
duced between  the  two  ends  of  the  cut  circuit,  or  poles,  a 
jet  of  electrical  molecules  which  is  called  the  voltaic  arc.  It 
was  the  first  known  of  the  different  electric  lights,  for  Sir  Hum- 
phry Davy  produced  it  before  1813.  To  possess  the  great 
brilliancy  which  characterizes  it,  the  voltaic  arc  should  con- 
tain a  large  number  of  material  particles  very  finely  divided 
and  brought  to  a  white  heat.  These  particles  are  torn  off  and 


HOW  THE  ELECTRIC  LIGHT  IS  PRODUCED.  33 

carried  along  by  the  current,  on  account  of  the  enormous 
temperature  of  the  severed  ends  of  the  circuit.  As,  among 
the  bodies  which  are  sufficiently  good  conductors,  it  is  car- 
bon which  supports  the  most  intense  heat,  and  which,  con- 
sequently, can  furnish  the  most  light,  it  is  that  which  has 
been  chosen  to  form  the  ends  of  the  circuit  (Fig.  15). 


FIG.  15. — The  two  poles  of  the  voltaic  arc. 

If  the  electric  current  succeeds  in  overcoming  the  resist- 
ance of  the  air,  it  is  because  the  gases  become  better  con- 
ductors as  they  are  heated,  which  naturally  happens  from 
their  contact  with  the  heated  electrodes.  Besides  this,  the 
layer  of  air  to  be  traversed  must  be  thin.  Now,  the  passage 


34  THE   VOLTAIC   ARC. 

of  the  electric  current  destroys  quite  rapidly  the  extremity 
of  the  electrodes  of  carbon,  so  that,  if  the  electrodes  are  not 
brought  together  in  exact  proportion  to  this  destruction,  the 
current  will  soon  cease  to  pass,  and  the  light  will  be  extin- 
guished. To  effect  this  approach  with  regularity,  regulators 
must  be  employed,  and  it  is  the  perfecting  of  them  that  has 
been  the  great  problem  of  this  kind  of  electric  lighting.  It 
may,  therefore,  be  properly  termed  the  "  regulator  system." 

Instead  of  placing  the  two  electrodes  of  carbon  one  above 
the  other,  which  necessitates  the  employment  of  a  regulator 
to  bring  them  together,  they  may  be  placed  side  by  side,  sep- 
arated by  a  solid  insulating  substance  which  will  volatilize 
at  the  same  rate  as  that  at  which  the  carbons  are  consumed 
under  the  action  of  the  voltaic  arc.  This  is  the  candle  sys- 
tem, from  the  name  given  by  M.  Jablochkoff  to  these  new 
apparatus  because  of  the  resemblance  between  the  method  of 
using  them  and  the  consumption  of  a  candle. 

We  have  said  that  the  voltaic  arc  was  produced  when  the 
circuit  traversed  by  the  electric  current  was  interrupted  ;  this 
rupture  of  the  circuit  should  not  be  done  too  rapidly,  or  it 
will  only  produce  a  spark,  a  species  of  flash  very  bright  and 
very  rapid.  The  two  poles  should  separate  so  slowly  that 
heating  will  take  place,  and  that  a  sort  of  chain  of  moving 
material  particles  will  be  formed,  torn  from  the  positive  and 
transported  to  the  negative  pole.  The  two  poles  reach  thus 
an  enormous  temperature,  nearly  4,000°  at  the  positive  and 
3,000°  at  the  negative  pole,  the  latter  only  being  heated  by  a 
secondary  cause,  which  we  shall  examine. 

The  true  sources  of  luminous  radiation  are  the  carbon- 
points,  and,  above  all,  the  points  where  the  passage  of  the 
electrical  molecules  are  concentrated ;  as  for  the  arc  itself, 
notwithstanding  its  high  temperature,  about  4,800°,  it  gives 
but  little  light,  and  the  light  which  it  gives  is  of  a  violet-blue. 
It  is  this  that  gives  to  electric  lighting  its  disagreeable  reflec- 
tions which  have  been  so  much  criticised,  and  which  are  re- 
duced as  much  as  possible  by  diminishing  its  length,  that  is 
to  say,  by  separating  the  carbons  only  the  distance  that  is 
indispensable,  and  which  is  naturally  in  proportion  to  the 
intensity  of  the  current. 

We  have  said  that  the  current  which  springs  from  the 
positive  pole  to  the  negative  one  tears  off  and  draws  with  it 
material  molecules  in  the  state  of  incandescence.  These  mole- 


HOW   THE  ELECTRIC  LIGHT  IS  PRODUCED.  35 

cules,  projected  against  the  other  pole,  heat  it  doubly  by  the 
heat  which  they  bear  with  them  and  by  the  shock  which  re- 
sults from  their  velocity  ;  but  this  species  of  bombardment  of 
one  pole  by  another  represents  a  mechanical  action,  and  cre- 
ates in  consequence  an  electro-motive  force.  The  enormous 
difference  of  temperature  of  the  two  poles  produces  another 
electro-motive  force,  and  both  working  together  give  rise  to 
a  counter-current,  which  in  its  turn  seizes  and  transports  par- 
ticles of  the  negative  to  the  positive  pole.  This  reactionary 
force  is  of  considerable  importance,  because  in  the  arc  pro- 
duced by  a  battery  of  forty  Bunsen  cells  it  has  been  found 
equal  to  twelve  cells  (Latschinoff) ;  with  another  battery  of 
twenty-six  Bunsen  cells  it  has  been  found  equal  to  nearly  ten 
cells  (Edlund) ;  finally,  M.  Leroux  has  been  able  to  prove  its 
existence,  and  to  measure  it  two  tenths  of  a  second  after  the 
rupture  of  the  current.  The  total  resistance  of  a  voltaic  arc 
is  thus  composed — first,  of  the  resistance,  properly  so  called, 
of  the  arc ;  and,  secondly,  of  that  which  is  created  by  the 
electro-motive  force  of  the  reaction. 

It  will  be  understood,  from  what  precedes,  that  the  posi- 
tive carbon  should  be  the  brightest,  because  the  light  emitted 
by  an  incandescent  body  rapidly  increases  with  its  tempera- 
ture. Besides,  the  consumption  of  the  two  poles  is  very  un- 
equal, and,  when  they  both  have  the  same  section,  the  positive 
is  consumed  twice  as  fast  as  the  other.  Finally,  numerous 
experiments  have  shown  that  the  resistance  of  the  arc  is  less 
when  the  positive  pole  is  the  uppermost ;  it  is  also  more  lu- 
minous, and  M.  Niaudet  has  found,  for  the  same  current,  a 
luminous  intensity  of  two  hundred  and  seventy-eight  Carcel 
burners  with  the  positive  carbon  uppermost,  and  two  hundred 
and  seventeen  only  with  the  positive  below.  Small  as  the 
mass  of  the  particles  transported  may  be,  does  it  not  seem 
that  their  weight  plays  a  part  in  this  difference  ? 

When  the  arc  is  produced  by  alternately  reversed  currents, 
the  consumption  is  equal  if  the  carbons  are  horizontal ;  if 
they  are  vertical,  the  upper  carbon  is  used  up  a  little  the 
quicker,  in  the  ratio  of  one  hundred  and  eight  to  one  hun- 
dred. The  current  of  warm  air  which  surrounds  it  raises  its 
temperature,  and  probably  the  force  of  gravity  assists  the 
separation  and  fall  of  a  greater  number  of  particles. 

The  resistance  of  the  arc  diminishes  as  its  length  dimin- 
ishes ;  but  at  the  same  time  the  temperature  is  lowered,  and 


36  THE  VOLTAIC   ARC. 

the  light  diminishes,  so  that,  to  keep  it  up  sufficiently,  more 
electrical  molecules  must  be  passed  through  the  polar  car- 
bons, or  else  the  section  of  the  carbons  must  be  consid- 
erably reduced,  which  are  then  'more  rapidly  consumed ; 
besides,  the  heat  spread  over  a  great  length  will  not  give 
enough  light. 

By  augmenting  the  dimensions  of  the  negative  carbon,  its 
consumption  is  retarded  ;  by  reducing  the  section  of  the 
positive  carbon,  and  by  restricting,  by  the  aid  of  a  properly 
adjusted  contact,  the  length  of  the  incandescent  portion,  the 
heating  is  concentrated  in  this  part,  and  enough  light  is  pro- 
duced, the  more  so  as  the  solution  of  continuity  which  always 
exists  at  the  point  of  contact  of  the  two  carbons  greatly  in- 
creases the  resistance.  It  follows  that  the  little  rod  of  posi- 
tive carbon  exhausts  itself  at  the  end  which  rests  upon  the 
other  carbon,  and  that  it  suffices  to  make  it  advance  so  as  to 
keep  up  the  contact  and  obtain  a  luminous  focus,  less  intense, 
it  is  true,  but  milder  and  more  agreeable  than  the  voltaic  arc 
because  of  its  fixity  and  its  regularity.  This  is  what  is  meant 
by  incandescence  in  the  open  air. 

Another  mode  of  using  the  voltaic  arc  consists  in  inter- 
posing in  its  passage  a  block  of  refractory  material  which 
becomes  the  true  source  of  light,  on  account  of  the  enormous 
temperature  which  it  may  attain.  With  this  arrangement, 
it  is  especially  the  heat  of  the  arc  which  is  utilized,  and  the 
polar  carbons  only  serve  to  produce  it.  The  yellow  color- 
ation of  the  light  thus  obtained  resembles  to  a  considerable 
extent  that  which  the  rays  of  the  sun  give  us,  whence  the 
name  of  solar  lamp  given  to  the  apparatus  serving  for  its 
production. 

Finally,  the  obstacle  opposed  to  the  passage  of  the  current 
can  consist  simply  in  a  sudden  diminution  of  the  conductivity 
of  the  circuit,  and  the  best  mode  of  obtaining  this  sudden 
diminution  is  to  diminish  the  conductor.  This  diminished 
part  should  be  formed  of  an  infusible  substance  of  high  re- 
sistance, such  as  a  fine  thread  of  platinum  or  a  very  thin 
filament  of  carbon.  This  thread  becomes  incandescent  on 
account  of  the  friction  of  the  electric  molecules  as  we  have 
described  above,  and,  if  care  be  taken  to  inclose  it  in  a  globe 
of  glass  completely  exhausted  of  air,  it  does  not  burn,  and 
lasts  a  very  long  time.  It  is  the  system  of  incanctescent  light- 
ing which  was  the  great  sensation  of  the  Exhibition  of  Elec- 


ELECTRICAL  UNITS.  37 

tricity  at  Paris — the  systems  of  Edison,  of  Maxim,  of  Swan, 
and  of  Lane-Fox. 

These  different  systems  exact  different  conditions,  and  are 
not  all  adapted  to  the  same  needs,  as  we  shall  see  further  on. 


CHAPTER  II.. 

ELECTRICAL   UNITS. 

[BEFOEE  proceeding  to  a  description  of  the  lamps  in  which 
the  current  is  utilized,  and  to  the  generators  by  which  it  is 
produced,  it  will  be  desirable  to  consider  the  relations  of  the 
electrical  elements  with  which  we  have  to  deal,  the  units  of 
measurement,  and  the  relations  these  bear  to  the  mechanical 
ones  of  force  and  work. 

Whenever  a  body  is  moved  against  any  force  opposing  its 
motion,  work  is  done,  and  its  amount  will  depend  upon  the 
intensity  of  the  force  and  the  distance  through  which  it  is 
overcome.  Thus,  if  we  lift  a  pound-weight  up  against  the 
force  of  gravity,  we  perform  a  certain  amount  of  work.  If 
we  raise  two  pounds  the  same  distance,  or  the  one  pound  to 
double  the  height,  we  shall  evidently  do  twice  as  much  work. 
Similarly,  work  will  be  done  in  overcoming  any  other  force 
than  gravity,  such  as  the  molecular  forces  of  chemical  attrac- 
tion, in  separating  the  constituent  elements  of  a  compound,  or 
magnetic  force,  in  drawing  a  piece  of  iron  and  a  magnet  asun- 
der, or  in  rotating  a  closed  coil  of  wire  in  front  of  the  poles 
of  a  magnet,  and  the  amount  of  this  work  will  always  be  ex- 
pressed by  the  product  of  the  force  by  the  distance  through 
which  it  is  overcome. 

A  body  is  said  to  possess  energy  when  it  is  capable  of 
doing  work,  either  in  consequence  of  the  motion  with  which 
it  is  endowed  or  of  its  position.  If  we  fire  a  ball  upward  from 
a  rifle,  it  possesses  the  power  of  doing  work  on  account  of  its 
motion.  It  is  then  said  to  possess  moving  or  kinetic  energy. 
As  it  rises  against  the  pull  of  gravity,  its  velocity,  and  conse- 
quently its  moving  energy,  constantly  grows  less,  until  at  the 
top  of  its  flight  it  has  wholly  disappeared.  The  energy  of  the 
ball  has  not,  however,  been  lost,  but  simply  transformed.  The 


38  THE  VOLTAIC  ARC. 

ball  now  has  energy  due  to  its  position,  and  in  falling  to  the 
earth  again  it  can  do  the  same  amount  of  work  as  that  .done  in 
projecting  it  upward.  As  long  as  the  ball  is  supported  in  its 
elevated  position,  it  evidently  retains  this  power  of  doing 
work.  Its  energy  is  potential,  and  may  be  called  upon  to 
perform  work  whenever  desired.  The  separated  elements  of 
a  chemical  compound  just  as  truly  possess  energy  of  position 
as  an  elevated  body.  Allow  them  to  unite,  and  their  potential 
energy  will  pass  into  kinetic,  and  the  work  of  separation  be 
returned  in  that  of  chemical  combination.  If  we  consider  the 
projected  ball  at  any  point  of  its  passage  upward,  we  shall  see 
that  what  it  has  lost  in  kinetic  energy  it  has  gained  in  poten- 
tial energy,  and  that  the  sum  of  these  two  is  throughout  its 
whole  flight  constant.  Considering  the  universe  as  a  whole, 
we  shall  find  a  like  condition  of  things.  Amid  all  the  multi- 
farious changes  of  the  material  universe,  the  sum  of  the  energy 
due  to  position  and  of  that  due  to  motion  remains  the  same. 
It  is  this  fact  which  is  expressed  by  the  great  generalization 
of  the  conservation  of  energy. 

Work  is,  therefore,  the  measure  of  the  expenditure  of 
energy — that  is,  the  transformation  of  energy  from  one  form 
to  another.  Conversely,  no  such  transformation  of  energy  can 
ever  take  place  without  the  performance  of  work.  The  abso- 
lute measure  of  a  force  is  the  velocity  it  can  impart  to  a  given 
mass  of  matter  in  a  given  time,  but  for  most  purposes  it  is 
convenient  to  determine  a  force  by  comparing  it  with  gravity. 
As  the  weight  of  a  body  measures  the  intensity  of  this  force 
at  any  given  place,  the  magnitude  of  any  force  can  therefore 
be  expressed  simply  by  a  weight,  and  the  amount  of  work  by 
the  product  of  a  weight  by  a  distance. 

Work  and  power  are  not  infrequently  used  as  equivalent 
terms,  though  there  is  an  important  difference  between  them. 
Work  has  reference  solely  to  the  amount  of  effort  necessary 
to  accomplish  a  given  result,  and  is  independent  of  time.  The 
same  amount  of  work  is  done  in  lifting  a  pound  one  foot  high, 
whether  this  be  performed  in  a  second  or  a  year.  Power,  on 
the  other  hand,  expresses  the  rate  of  doing  work,  and  is  evi- 
dently greater,  the  shorter  the  time  in  which  a  given  amount 
of  work  is  performed. 

We  have  seen  in  the  preceding  chapter  that,  whenever  we 
connect  two  points  which  are  at  different  potentials  by  a  con- 
ductor, a  (current  of  electricity  will  flow  from  the  point  of 


ELECTKICAL  UNITS.  39 

higher  to  the  one  of  lower  potential.  A  difference  of  poten- 
tial is  analogous  to  a  difference  of  level  of  water,  and  just  as 
work  must  be  done  in  raising  water  from  the  lower  to  the 
higher  level,  so  work  must  be  done  in  raising  electricity  from 
the  lower  to  the  higher  electrical  level.  The  water,  in  falling, 
is  able  to  perform  the  work  done  in  lifting  it  ;  and  the  elec- 
tricity, that  done  in  raising  it  to  the  higher  potential.  The 
amount  of  this  work  is  in  each  case  the  quantity  multiplied 
by  the  height  from  which  it  fell.  In  the  case  of  electricity, 
the  difference  of  electrical  level  is  expressed  in  terms  of  the 
force  or  pressure  due  to  it.  This  force  is  termed  electro- 
motive force.*  The  work  done,  then,  by  any  given  quantity 
of  electricity,  Q,  falling  through  a  difference  of  potential,  E, 
is  E  Q.  As  the  strength  or  intensity  of  the  current  expresses 
the  rate  at  which  electricity  moves  through  a  circuit  —  the 
number  of  units  of  electricity  that  pass  a  given  point  in  a 
given  time  —  the  product  of  the  strength  of  the  current  by 
the  electro-motive  force  will  evidently  express  the  rate  of  the 
performance  of  work  —  that  is,  the  power. 

The  intensity  of  the  current  in  any  electrical  circuit  will 
not  depend  solely  upon  the  electro-motive  force  impelling  it, 
but  will  also  depend  upon  the  resistance  offered  to  its  pas- 
sage. There  are,  therefore,  in  any  electrical  circuit,  three 
elements  to  be  taken  into  consideration  —  the  intensity  of 
the  current,  the  electro-motive  force,  and  the  resistance  — 
the  relation  of  which  to  each  other  is  a  very  simple  one, 
which  is  expressed  by  a  formula  known  as  Ohm's  law.  De- 
noting the  intensity  of  the  current  by  C,  the  electro-motive 
force  by  E,  and  the  resistance  by  R,  this  formula  is  — 


This  formula  shows  us  that  the  strength  of  the  current  that 
will  flow  through  any  circuit  will  be  directly  in  proportion  to 
the  electro-motive  force,  and  inversely  as  the  resistance  of  the 
circuit.  In  applying  the  formula  in  any  particular  case,  ifc 
must  be  borne  in  mind  that  the  electro-motive  force  and  resist- 
ance refer  to  the  same  circuit,  or  to  the  same  part  of  it  —  that 
is,  that  R  represents  the  resistance  of  the  same  part  of  the 
circuit  of  which  E  represents  the  difference  of  potential. 

*  The  term  electrical  pressure  is  coming  into  use  as  a  substitute  for  this.  It 
has  the  great  advantage  of  expressing  this  electrical  conception  in  terms  of  an 
already  familiar  one. 


40  THE  VOLTAIC   ARC. 

MECHANICAL  UNITS. 

To  compare  different  quantities  it  is  evident  that  we  must 
have  a  unit  in  terms  of  which  they  can  be  expressed.  The 
fundamental  units  upon  which  all  others  may  be  made  to  de- 
pend are  those  of  mass,  length,  and  time.  Until  recently  there 
have  been  no  units  of  these  quantities  universally  agreed 
upon.  In  England  and  the  United  States  the  unit  of  weight 
most  generally  employed  is  the  pound,  that  of  length  the 
foot,  and  that  of  time  the  second  or  the  minute  ;  while  in 
France  the  first  of  these  is  the  kilogramme  (2  '2  pounds),  and 
the  second  the  metre  (39  '37  inches).  In  the  former  countries  the 
unit  of  work  most  commonly  employed  is  the  work  required 
to  raise  one  pound  one  foot,  termed  the  foot-pound,  and  that 
of  power,  the  horse-power,  equivalent  to  550  foot-pounds  per 
second,  or  33,000  foot-pounds  a  minute.  In  France  the  unit 
of  work  is  the  kilogrammetre,  and  that  of  horse-power  (force 
de  cTienal)  75  kilogrammetres  per  second,  equal  to  542^  in- 
stead of  550  foot-pounds  per  second. 

The  need  of  a  uniform  system  of  units  had  long  been  felt, 
and  such  a  system  was  finally  adopted  by  the  International 
Congress  of  Physicists,  at  Paris,  in  1881.  This  system  is 
known  as  the  centimetre-gramme-second,  or,  more  briefly,  as 
the  C.  G.  S.  system,  so  named  from  the  units  of  length,  mass, 
and  time. 

In  it  the  unit  of  force,  termed  the  dyne,  is  that  force 
which,  acting  upon  a  mass  of  one  gramme  for  one  second,  is 
able  to  give  it  a  velocity  of  one  centimetre  per  second.  This 
unit,  it  will  be  observed,  is  independent  of  the  varying  force 
of  gravity,  but  it  can  readily  be  expressed  in  it  by  taking  ac- 
count of  the  amount  of  this  force  at  any  given  place.  The 
value  of  gravity  usually  adopted  is  that  at  Paris,  which  is 
able  to  impart  to  one  gramme  a  velocity  of  981  centimetres  per 
second,  so  that  a  gramme  is  equal  to  981  dynes,  and  a  dyne  to 
-J^Y  of  a  gramme.  From  what  has  already  been  said  it  will 
be  readily  understood  that  the  unit  of  work  is  the  dyne-centi- 
metre— that  is,  the  product  of  the  dyne  by  a  centimetre.  It 
is  termed  the  erg.  Since  a  kilogramme  is  equal  to  1,000 
grammes,  this  latter  to  981  dynes,  and  a  metre  to  100  centi- 
metres, the  kilogrammetre  is  evidently  equal  to  (981  X  1000  X 
100)  98,100,000  ergs.  The  foot-pound  is  in  like  manner  con- 
verted into  ergs  by  multiplying  the  product  of  the  equivalent 


ELECTRICAL  UNITS.  41 

of  the  pound  in  grammes  (453 -6)  by  the  equivalent  of  the 
foot  in  centimetres  (30 -48),  and  this  by  the  number  of  dynes 
(981)  in  a  gramme.  It  is,  therefore,  equal  to  (453'6  X  30-48 
X981)  13,563,000  ergs.  The  French  horse-power,  equivalent 
to  542|  foot-pounds,  or  75  kilogrammetres,  becomes  in  the 
new  unit  of  work  equal  to  7,357,500,000,  and  the  English 
horse-power,  equivalent  to  550  foot-pounds,  or  7G  kilo- 
grammetres, equal  to  7,460,000,000  ergs  per  second.  These 
are  usually  written  735*75  X  107,  and  746  X  101 

HEAT  UNITS. 

To  raise  the  temperature  of  a  body — say,  that  of  a  pound 
of  water  one  degree  Fahrenheit — evidently  requires  the  ex- 
penditure of  energy.  The  amount  of  heat  requisite  gives  us 
a  unit  by  means  of  which  we  can  compare  the  heat  expended 
in  any  other  case,  but  does  not  give  us  a  basis  for  comparing 
the  expenditure  of  energy  in  the  form  of  heat  with  that  in 
other  forms.  To  be  able  to  do  this  we  must  know  the  relation 
existing  between  heat-  and  mechanical  energy,  so  that  the 
former  can  be  expressed  in  terms  of  work.  This  relation  was 
established  some  forty  years  ago  by  the  labors  of  the  German 
physician,  Mayer,  and  the  English  physicist,  Joule.  By  a 
series  of  careful  experiments,  Joule  showed  that  the  amount 
of  heat  necessary  to  raise  a  pound  of  distilled  water  one  de- 
gree of  the  Fahrenheit  scale,  would  be  sufficient,  if  converted 
into  mechanical  energy,  to  raise  a  weight  of  772  pounds  one 
foot  high.  The  number  expressing  the  relation  between  heat 
and  work  is  termed  the  mechanical  equivalent  of  heat,  and 
is  frequently  spoken  of  as  Joule's  equivalent.  Evidently  its 
value  will  vary  with  the  units  of  work  and  temperature 
adopted.  When  the  degree  is  that  of  the  centigrade  scale 
(f  that  of  the.  Fahrenheit),  this  equivalent  becomes  equal  to 
1,390  foot-pounds;  and,  when  the  unit  of  work  is  the  kilo- 
grammetre,  and  of  temperature  the  centigrade  degree,  it 
becomes  424  kilogrammetres. 

In  the  English-speaking  world  the  heat  unit  has  usually 
been  the  pound-degree,  the  latter  being  measured  on  the 
Fahrenheit  scale ;  while  in  France  the  kilogramme-degree, 
the  latter  reckoned  on  the  centigrade  scale,  was  common. 

The  gramme  as  the  unit  of  weight  and  the  centigrade  de- 
gree as  the  unit  of  temperature  have  for  a  considerable  time 
been  in  use  in  all  countries  in  scientific  work.  Their  use  was 


42  THE  VOLTAIC  ARC. 

ratified  by  the  Paris  Congress,  and  the  heat  unit  of  the  C.G.S. 
system  is  therefore  the  gramme-degree.  It  is  termed  the 
calorie,  and  its  mechanical  equivalent  is  equal  to  42,000,000 
ergs,  written  4'2  X  107. 

ELECTEICAL  UNITS. 

Electricity  can  be  measured  in  two  different  ways,  corre- 
sponding to  the  two  different  classes  of  electrical  phenomena 
with  which  we  are  acquainted — those  of  statical  and  those 
of  current  electricity.  The  readiest  way  of  measuring  the 
strength  of  an  electric  current  is  by  its  magnetic  effects,  and 
the  electric  quantities  in  dynamical,  or  current,  electricity  are, 
therefore,  measured  electro-magnetically.  It  is  this  system 
which  alone  concerns  us  here,  but,  for  the  sake  of  clearness, 
it  will  be  desirable  to  give  a  brief  outline  of  the  electro-static 
system  of  measurement. 

As  is  well  known,  a  body  charged  with  electricity  will 
attract  another  body  with  an  unlike,  and  repel  one  with  a 
like,  charge.  The  amount  of  this  attractive  or  repulsive  force 
will  depend  upon  the  amount  of  the  charge  and  the  distance 
of  the  bodies  asunder.  A  unit  of  statical  electricity  can, 
therefore,  be  very  readily  defined  with  reference  to  these  con- 
ditions. It  is  that  quantity  of  electricity  which  repels  a 
similar  and  equal  quantity,  at  a  unit  distance  (one  centimetre), 
with  a  force  of  one  dyne. 

The  difference  of  potential  between  any  two  points  is 
measured  by  the  work  which  must  be  done  to  move  a  quan- 
tity of  electricity  from  the  lower  to  the  higher.  A  unit  dif- 
ference of  potential  is,  therefore,  that  difference  of  potential 
which  must  exist  between  two  points  in  order  that  a  unit  of 
work  will  be  done  in  conveying  a  unit  of  positive  electricity 
from  the  lower  to  the  higher.  A  unit  of  work  will,  of  course, 
be  performed  by  a  unit  of  electricity  in  falling  through  this 
unit  difference  of  potential. 

A  unit  current  in  this  measure  is  one  which  conveys  an 
electro-static  unit  of  quantity  per  second,  and  a  circuit  of 
unit  resistance  is  one  in  which  the  number  of  units  of  quan- 
tity which  pass  in  a  second  is  equal  to  the  number  of  units  of 
difference  of  potential  between  its  ends — that  is,  in  the  equa- 

Tjl 

tion  E,  =  — ,  where  R  =  the  resistance,  E  the  difference  of  po- 
\j 

tential,  and  C  the  strength  of  current,  R  is  unity  when  E  =  C. 


ELECTRICAL  UNITS.  43 

In  the  electro-magnetic  system  of  measurement  the  units 
of  these  different  quantities  bear  the  same  relation  to  each 
other — that  is,  the  unit  current  will  flow  through  a  circuit 
having  a  unit  difference  of  potential  between  its  ends,  when 
it  has  a  unit  resistance,  and  the  unit  quantity  is  the  amount 
of  electricity  conveyed  in  a  second  by  a  unit  current,  but  they 
have  different  absolute  values. 

In  adopting  units  of  current  strength  and  quantity,  we 
may  determine  either  unit  by  reference  to  some  particular 
standard,  and  then  express  the  other  in  terms  of  this ;  just  as, 
in  the  case  of  a  current  of  water,  we  may  take  the  unit  of 
quantity  to  be  a  gallon,  and  then  define  a  unit  current  as  one 
which  conveys  a  gallon  a  second ;  or  we  may  adopt  some  given 
current  as  the  unit  of  current,  and  then  define  the  unit  of 
quantity  as  the  quantity  delivered  by  this  current  per  sec- 
ond. The  first  of  these  methods  is  followed  in  electro-static 
measurement,  where  the  unit  quantity  is  determined  by  refer- 
ence to  its  effect  upon  a  like  quantity  ;  the  second  is  adopted 
in  electro-magnetic  measurements.  In  this  system  the  strength 
of  the  current  is  defined  with  reference  to  its  effect  upon  a 
magnet-pole  in  its  vicinity.  This  effect  will  depend  upon  the 
strength  of  the  magnet-pole,  of  the  current,  the  length  of  the 
circuit,  and  the  distance  of  the  circuit  from  the  pole.  Evi- 
dently, to  get  an  expression  for  a  unit  strength  of  current, 
each  of  these  quantities  must  be  unity.  The  unit  of  current- 
strength,  therefore,  becomes  that  current  every  centimetre  of 
whose  length  acts  with  a  force  of  one  dyne  upon  a  unit 
magnet-pole  at  a  distance  of  one  centimetre  (a  unit  magnet- 
pole  is  one  which  will  repel  an  equal  like  pole  with  a  force  of 
one  dyne  at  a  distance  of  a  centimetre).  This  condition  is 
realized  when  the  wire  conveying  the  current  is  bent  into  a 
circle  of  one  centimetre  radius,  at  the  center  of  which  is 
placed  the  unit  magnet-pole.  Then,  when  a  unit  current  flows 
through  the  circuit,  every  centimetre  of  its  length  will  act 
upon  the  central  magnet-pole  with  a  force  of  one  dyne.  The 
unit  quantity,  as  before  stated,  is  the  quantity  conveyed  by 
this  unit  current  in  one  second,  and  the  unit  electro-motive 
force  is  in  this  case,  as  in  that  of  electro-static  measure,  de- 
termined by  the  condition  that  it  requires  the  expenditure  of 
one  erg  of  work  to  raise  a  unit  of  quantity  through  a  unit  of 
potential.  As,  however,  the  electro-magnetic  unit  of  quan- 
tity is  much  larger  than  the  electro-static,  the  electro-magnetic 


44  THE  VOLTAIC  ARC. 

unit  of  potential  is  correspondingly  smaller.  The  electro- 
magnetic unit  of  resistance  is  determined  by  the  same  condi- 
tion as  that  of  the  electro-static  unit.  As  the  unit  quantity 
of  electricity  in  falling  through  a  unit  difference  of  potential 
performs  one  erg  of  work,  it  is  clear  that  a  unit  electro-motive 
force  does  a  unit  of  work  per  second  in  a  circuit  of  unit  resist- 
ance. 

One  more  unit  remains  to  be  noticed.  This  is  the  unit  of 
capacity.  This  term  denotes  the  ability  of  a  body  to  hold  a 
charge  of  electricity,  and  this  capacity  is  measured  by  the 
quantity  of  electricity  at  unit  potential  which  it  can  contain. 
When  this  quantity  is  unity,  the  body  has  unit  capacity. 

PEACTICAL  UNITS. 

Most  of  the  above  units  are  too  small  for  use  in  practice. 
Another  system  of  units,  based  upon  them,  termed  practical 
units,  has  therefore  been  devised.  In  this  system  the  unit  of 
electro-motive  force  is  termed  the  wit,  in  honor  of  the  Italian 
physicist,  Yolta.  It  is  equal  to  100,000,000,  written  108,  C.  G.  S. 
units.  The  unit  of  resistance,  termed  the  ohm,  is  equal  to 
109  C.  G.  S.  units.  It  is  equal  to  the  resistance  of  a  wire  of 
pure  copper  one  millimetre  in  diameter  and  forty-eight  metres 
long.  The  unit  of  current  adopted  is  the  current  produced 
in  a  circuit  of  one  ohm  resistance  by  a  difference  of  potential 
of  one  volt.  Its  value  is  evidently  TV  that  of  the  C.  G.  S.  unit, 

E 

since  C  =  — ,  and  the  practical  units  of  E  and  R  are  E  X  108 
K 

and  R  X  109.  It  is  written  1(H.  It  was,  previous  to  the  Paris 
Congress,  denoted  in  England  and  this  country  by  the  name 
weber.  A  unit,  -^  of  this  was  in  use  in  Germany  under  the 
same  name.  The  congress,  therefore,  in  order  to  avoid  con- 
fusion, substituted  for  this  name  that  of  ampere.  The  unit 
of  quantity,  which  is  the  quantity  conveyed  by  a  current  of 
one  ampere  in  a  second,  is  termed  the  coulomb.  Its  value  is 
evidently  -fa  of  the  C.  G.  S.  unit.  The  practical  unit  of  work 
is,  therefore,  the  volt-coulomb,  and  of  power,  the  volt-ampere. 
The  former  is  equal  to  108  X  10"1  =  107  ergs,  and  the  latter  to 
107  ergs  per  second. 

Since  the  English  horse-power  is  equal  to  746  XlO7  ergs 
per  second,  a  volt-ampere  is  equal  to  -^  of  it,  and  to  ^-^.-^ 
of  a  force  de  cTieval,  and  the  horse-power  developed  by  any 
number  of  amperes,  C,  falling  through  a  difference  of  poten- 


ELECTEICAL   UNITS.  45 

F  C  "F  O 

tial,  E,  is  therefore  -^—  in   English,  and  in  French 

measure.  The  equivalent  of  a  horse-power  in  electrical  meas- 
ure (746  or  735 '75  volt-amperes)  is  commonly  spoken  of  as 
an  " electrical  horse-power,"  or  a  " horse-power  of  current." 
In  his  presidential  address  in  1882,  before  the  British  Associa- 
tion, Sir  William  Siemens  proposed  that  the  practical  unit 
of  power,  the  volt-ampere,  be  termed  the  watt,  in  honor  of 
James  Watt,  and  this  suggestion  has  been  very  generally 
acted  upon.  He  also  proposed  the  name  of  Joule  to  designate 
the  heat  produced  in  one  second  by  a  current  of  one  ampere 
in  a  circuit  of  a  resistance  of  an  ohm.  This  unit,  it  will  be 
seen,  is  equivalent  to  the  volt-coulomb,  since  this  latter  is  the 
work  done  in  one  second,  in  a  circuit  of  one  ohm  resistance, 
by  a  current  of  one  ampere,  and  the  whole  of  the  work  done 
by  the  current  in  this  case  is  spent  in  the  production  of  heat. 
Its  value  is,  therefore,  107  ergs,  and,  since  a  heat  unit  is  equal 
to  4  '2  X  107  ergs,  it  is  equal  to  ¥^  —  '24  of  a  calorie. 

The  unit  of  capacity  is  termed  the  farad,  in  honor  of  Fara- 
day. Since  the  capacity  is  determined  by  dividing  the 
quantity  of  the  charge  by  its  potential,  this  unit  is  equal  to 

O      10—1  1 

^  —  — —  =  10~9,  or  —  of  the  C.  G.  S.  unit  of  capacity.    As 

Jjj       10  10 

this  unit  is  very  large,  the  one-millionth  part  of  it,  the  micro- 
farad, is  commonly  used  in  practice.  It  is  equal  to  10"6  farad, 
and  10~15  C.  G.  S.  units. 

The  following  summary  of  these  units  will  facilitate  refer- 
ence to  them,  and  help  the  comprehension  of  their  relations  : 

Unit  of  force  =  dyne. 

Unit  of  work  —  erg,  =  dyne  X  centimetre. 

Unit  of  heat  =  calorie  =  4'2  X  107  ergs. 

Yolt  =  practical  unit  of  electro-motive  force  =  108  C.  G.  S. 
units. 

Ohm  =  practical  unit  of  resistance  —  109  C.G.S.  units. 

Ampere  =  practical  unit  of  intensity  of  current  =  10"1  C. 
G.  S.  units. 

Coulomb  =  practical  unit  of  quantity  =  1Q-1  C.  G.  S.  units. 

Farad  —  practical  unit  of  capacity  =  10~9  C.  G.  S.  units. 

Joule  =  electrical  unit  of  work  =  volt-coulomb  =  107  ergs 
=  '24  calorie. 

Watt  —  electrical  unit  of  power  =  volt-ampere  =  -fa  horse- 
power =  107  ergs  per  second. 


46  THE  VOLTAIC  ARC. 

English  horse-power  —  550  foot-pounds  =  746  X  107  ergs 
per  second  =  746  watts. 

French  horse-power  =  542J  foot-pounds  —  735*75  X  107 
ergs  per  second  =  735*75  watts.] 


CHAPTER  III. 

THE  ARC-LAMP  CARBONS. 

THE  first  condition  to  be  fulfilled  in  making  the  voltaic 
arc  a  good  source  of  light,  is  to  make  it  play  between  two 
electrodes,  capable  of  furnishing  to  this  arc  the  minute  in- 
candescent particles  which  give  it  its  immense  brilliancy. 
Carbon  only  seems  adapted  for  this  end,  and  it  was,  in  fact, 
with  electrodes  of  carbon  that  Sir  Humphry  Davy  produced 
the  first  voltaic  arc.  But  there  are  ma4y  kinds  of  carbons, 
and  the  choice  of  this  material  is  not  the  least  difficult  of  the 
questions  that  have  arisen  in  electric  lighting,  because  the 
two  electrodes  should  combine  qualities  that  are  different  and 
often  even  opposite  ones. 

After  his  famous  experiment  in  1813,  Sir  Humphry  Davy 
employed  pieces  of  wood-charcoal  quenched  in  water  or  in 
mercury.  But  these  pencils  of  soft  carbon  were  too  rapidly 
consumed  to  afford  a  light  of  any  definite  duration,  even  in 
operating  in  a  closed  vessel,  almost  completely  exhausted  by 
the  air-pump,  as  Davy  attempted  to  do,  in  spite  of  the  incon- 
venience of  this  arrangement.  Carbons  were  elsewhere  sought 
for  that  would  be  more  compact  and  consequently  more  du- 
rable, and  which  were  also  capable  of  being  formed  into  pen- 
cils without  breaking  or  going  into  powder. 

Foucault,  one  of  the  greatest  French  physicists  of  this 
century,  first  had  the  idea  of  using  the  carbon  which  is  de- 
posited on  the  sides  of  gas-retorts.  This  carbon,  slowly 
formed,  is  more  durable  than  all  the  others,  and  burns  much 
more  slowly,  so  that  Foucault  succeeded  in  obtaining  a  voltaic 
arc  of  much  longer  duration. 

But  gas-carbon  was  anything  but  perfect,  especially  from 
not  being  homogeneous.  It  was  mixed  with  earthy  substances, 
particularly  silica,  which  melted  and  often  made  the  carbon 


THE  ARC-LAMP  CARBONS.  47 

sparkle  by  causing  minor  variations  in  the  light,  which  already 
was  too  unsteady.  Sometimes,  too,  the  silicious  matter  vola- 
tilized and  projected  jets  of  vapor  which  were  better  conduct- 
ors of  electricity  than  the  air,  even  when  hot ;  in  this  case  the 
electric  discharge  followed  by  preference  these  vapors,  and 
passed  into  obscurity,  as  no  solid  particles  were  present  to 
produce  incandescence.  It  was  so  much  loss  of  light. 

There  are,  without  doubt,  in  these  carbonaceous  deposits 
some  parts  more  homogeneous  than  others,  and  to-day  the  lo- 
cality of  these  superior  parts  can  be  found  with  greater  cer- 
tainty than  formerly,  and  the  pencils  for  electrodes  can  be 
taken  thence.  But,  in  spite  of  everything,  it  is  very  hard  to 
avoid  all  traces  of  silica.  Besides,  it  takes  so  long  to  form 
carbon  in  the  gas-retorts  that  it  would  be  impossible  to  pro- 
cure enough  from  that  source  to  give  to  the  voltaic-arc  system 
of  illumination  the  development  that  has  been  anticipated 
for  it. 

An  artificial  carbon,  therefore,  must  be  made  to  supple- 
ment the  deficient  supply  of  gas-carbon.  Bunsen  was  the 
first  to  make  it  in  1838  or  1840,  although  for  another  purpose. 
He  was  in  search  of  a  suitable  material  of  which  to  form  the 
cylinder  of  carbon  that  constitutes  an  essential  feature  of  his 
nitric-acid  cell. 

Among  other  trials  he  thought  of  agglomerating  with  glue 
dry  bituminous  coal  finely  pulverized,  and  of  baking  in  a  fur- 
nace the  blocks  thus  obtained.  But  these  blocks  split.  To 
increase  their  solidity  he  conceived  the  idea  of  immersing  them 
in  a  sugar- sirup  which  would  fill  all  the  cracks,  and  then  of 
baking  them  a  second  time.  The  sugar  was  carbonized  in 
this  second  baking,  and  completely  filled  all  the  pores,  so  as 
to  furnish  as  compact  a  carbon  as  the  gas-carbon,  but  purer 
and  much  more  homogeneous.  If  necessary,  they  could  be 
heated  a  third  time  after  a  third  immersion,  to  complete  the 
effect  of  the  second  one. 

In  1846  two  Englishmen,  Staite  and  Edwards,  patented  a 
mode  of  manufacture  analogous  to  that  of  Bunsen,  but  they 
specified  particularly  that  they  wished  to  obtain  carbons  for 
the  electric  light.  Soon  other  improvements  were  effected. 
In  1849  Le  Moult  added  coal-tar  to  the  sugar-sirup,  and  used 
different  kinds  of  powdered  carbon  which  he  heated  for  thirty 
hours,  and  then  purified  by  immersion  in  acids.  In  1852  Wat- 
son and  Slater  preferred  twigs  of  wood  purified  by  lime,  sev- 


48 


THE  VOLTAIC  ARC. 


eral  times  heated,  after  having  been  dipped  first  in  alum,  and 
then  in  molasses. 

Later  on,  in  1857,  Lacassagne  and  Thiers  returned  to  gas- 
carbon  ;  but  they  purified  it  by  a  number  of  successive  op- 
erations which  re- 
moved its  silicious 
and  other  impuri- 
ties. The  light  was 
not  so  unsteady  ; 
unfortunately,  the 
carbon,  whose  com- 
pactness was  de- 
stroyed by  this 
laborious  purifica- 
tion, permitted 
sparks  and  even 
cinders  to  escape. 

About  the  same 
time,  an  old  chemist 
of  the  Ecole  Cen- 
trale,  M.  Jacque- 
lain,  made  a  very 
pure  artificial  car- 
bon with  the  tar 
derived  from  the 
distillation  of  coal 
or  of  schist ;  the 
intensity  of  light 
these  carbons  gave 
was  one  quarter 
greater  than  that 
afforded  by  the 
others ;  but  the 
blocks  thus  made 
had  to  be  cut  up, 
a  long  and  costly 

operation,  on  account  of  the  hardness  of  the  carbon.  A  little 
later  M.  Archereau  obtained  also  excellent  results  in  mixing 
magnesia  with  carbon-dust.  He  first  conceived  the  idea  of 
compressing  the  paste  by  passing  it  through  a  draw-plate 
such  as  is  used  for  wire-making,  a  process  followed  to-day 
by  all  manufacturers. 


FIG.  16.— Draw-plate,  with  hydraulic  press,  for  making  arti- 
ficial carbons. 


THE   ARC-LAMP  CARBONS.  49 

Toward  1876,  M.  F.  Carre  introduced  important  improve- 
ments into  this  manufacture,  notably  the  use,  for  driving  the 
paste  through  the  draw-plate,  of  a  very  powerful  hydraulic 
press  (Fig.  16).  The  carbon-paste  was  composed  of  fifteen 
parts  of  very  pure  coke,  reduced  to  extremely  fine  powder,  five 
parts  of  calcined  lamp-black,  and  seven  or  eight  parts  of  sugar- 
sirup  mixed  with  a  little  gum.  The  whole  was  ground  up 
with  exactly  the  right  quantity  of  water  to  form  a  paste  of 
the  desired  consistency,  and  intimately  mixed  by  machinery. 
After  the  passage  through  the  draw-plate,  which  was  facili- 
tated by  heating  the  body  of  the  press,  the  pencils  were  ar- 
ranged on  grooved  tablets  covered  with  charcoal-dust,  and 
these  tablets  were  introduced  into  a  furnace  where  they  were 
maintained  for  about  five  hours  at  a  cherry-red  heat.  The  pen- 
cils were  next  plunged  into  a  sirup  of  boiling  caramel,  dried, 
and  reheated  in  crucibles,  but  at  a  higher  temperature  :  this 
was  called  nourishing  them.  These  two  operations  were  re- 
peated until  the  pencils  had  acquired  the  necessary  density 
and  hardness,  and  they  were  finally  dried  in  a  stove. 

M.  E.  Carre,  who  worked  under  his  brother's  patents,  suc- 
ceeded in  making  continuously  pencils  of  more  than  a  metre 
in  length,  and  of  all  sizes.  In  some  the  diameter  was  reduced 
to  a  millimetre.  They  were  perfectly  straight  and  of  remark- 
able solidity.  The  results  he  obtained  have  done  much  to  con- 
tribute to  the  success  of  electric  lighting. 

In  1877  M.  Gaudoin  also  succeeded  in  furnishing  carbons  of 
excellent  quality,  which  many  engineers  prefer  even  to  Carre's 
carbons,  although  the  last  are  most  widely  used  in  France, 
and  are  exported  abroad,  especially  to  England. 

In  Germany,  carbons  made  by  the  house  of  Siemens  are 
principally  used,  which  are  exported  also  to  other  countries. 
They  give  very  good  results,  especially  as  regards  fixity  of 
the  light ;  but  their  composition  and  mode  of  manufacture  are 
kept  secret. 

The  last  improvements  introduced  in  France  are  due  to  M. 
Napoli,  who  especially  had  in  view  pencils  destined  for  open- 
air  incandescent  burners  of  the  Reynier-Werdermann  type. 
His  principal  object  was  to  obtain  a  carbon  that  would  burn 
more  slowly  than  the  Carre  or  Gaudoin  carbons,  so  that  the 
lighting  could  last  for  a  longer  period  without  renewal  of  the 
carbon-pencils.  He  succeeded,  in  fact,  in  decreasing  the  con- 
sumption of  the  carbons  to  only  five  centimetres  per  hour  of 


50 


THE  VOLTAIC  ARC. 


lighting,  while  the  Carre  carbons  burned  five  times  faster  under 
the  same  conditions,  that  is  to  say,  consumed  twenty  five  cen- 
timetres of  length,  or  one  and  a  half  metres  per  one  evening's 
lighting  of  six  hours'  duration. 

This  result  was  due  to  the  materials  employed  and  to  the 
means  used  to  unite  them  intimately. 

M.  Napoli  attributed  the  rapidity  of  consumption  of  the 


FIG.  17. — Curved  nozzle  draw-press 
of  M.  Napoli  (vertical  section). 


FIG.  18. — Cylinder  for  nourishment 
of  the  carbons  under  pressure, 
by  M.  Napoli' s  method. 


carbons  to  the  original  difference  between  its  constituent  ele- 
ments, namely,  the  agglomerating  liquid  and  the  solid  matter 
it  was  to  agglomerate  ;  a  difference  which  did  not  disappear 


THE  ARC-LAMP  CARBONS.  51 

at  all  during  the  fabrication,  and  which  thus  prevented  the 
perfect  homogeneity  of  the  carbon-pencil  obtained.  He  chose 
accordingly,  for  agglomerating  and  solid  material,  two  sub- 
stances of  identical  origin — for  one,  the  tar  of  bituminous 
coal ;  for  the  other,  the  coke  left  as  residue  from  the  distilla- 
tion of  this  tar  at  a  low  red-heat,  which  coke,  before  using, 
was  reduced  into  very  fine  powder,  which  was  carefully  sifted. 

The  paste  employed  consists  of  three  parts  of  coke  and 
only  one  of  tar.  M.  Napoli  strove  to  reduce,  as  far  as  pos- 
sible, the  proportion  of  agglomerant  to  avoid  the  shrinkage 
during  ignition  of  the  rods,  which  often  caused  cracks.  This 
paste  was  but  slightly  fluid,  so  that  he  had  to  employ  a  draw- 
ing-machine of  curved  shape  (Pig.  17)  for  forming  his  pencils. 

To  still  further  nourish  the  carbons  in  spite  of  the  con- 
siderable density  they  already  possessed,  he  placed  them 
in  a  special  cylinder  (Fig.  18),  where  alternately  a  vacuum 
could  be  produced  or  the  pressure  of  a  steam-boiler  admitted. 
This  cylinder  was  itself  surrounded  by  a  double  jacket,  into 
which  steam  was  introduced  to  heat  it  to  a  proper  tempera- 
ture during  the  operation.  When  the  carbons  had  been 
placed  in  the  cylinder,  a  vacuum  was  produced  there  which 
caused  the  air  condensed  in  their  pores  to  be  expelled  ;  then 
the  nourishing  liquid  was  introduced,,  on  which  steam-pressure 
was  made  to  act  which  drove  it  into  the  pores  exhausted  of 
air ;  finally,  when  the  liquid  nourisher  had  run  out,  a  jet  of 
steam  driven  through  the  bundle  of  rods  wiped  off  their  sur- 
face just  like  a  moistened  rag  in  the  hands  of  a  dish-washer. 

The  tout  ensemble  of  the  operations  may  be  seen  in  Fig. 
19,  which  shows  the  temporary  workshop  of  M.  Napoli,  Rue 
des  Martyrs,  Paris.  In  front,  the  grooved  tablets  are  spread 
out,  holding  the  carbon-rods ;  on  the  left  appear  the  rever- 
beratory  furnaces  where  they  are  reheated  ;  then  the  drawing- 
machine,  with  the  hydraulic  press  that  forms  them,  and,  fur- 
ther back,  the  cylinder  which  nourishes  them  under  pressure. 
At  a  distance  is  seen  the  receptacle  in  which  the  mixture  of 
substances  is  made,  by  the  side  of  the  engine  which  furnishes 
steam  and  drives  the  whole  machinery  of  the  workshop. 

To  indicate  the  importance  of  a  good  choice  of  carbons,  it 
is  enough  to  give  the  result  of  several  comparative  experi- 
ments. The  source  of  electricity  which  could  furnish  a  light 
equal  to  one  hundred  and  three  Carcel  lamps,  with  retort  or 
gas-carbon  pencils,  gives  one  hundred  and  twenty  Carcels 


THE  ARC-LAMP  CARBONS. 


53 


with  Archereau's  carbons,  and  one  hundred  and  eighty  with 
Carre' s  carbons.  It  is  claimed  that  Gaudoin's  carbons  will  go 
still  further,  and  will  give  as  much  as  two  hundred  or  two 
hundred  and  ten  Carcels,  or  double  that  which  retort-carbon 
gives  under  the  same  condi- 
tions. 

If  artificial  carbon  possesses 
the  qualities  necessary  for  the 
production  of  the  electric  light, 
it  has  the  inconvenience  of  be- 
ing a  very  poor  conductor  ;  for 
equal  dimensions  its  resistance 
is  much  greater  than  that  of 
pure  copper,  and  it  is  very  im- 
portant not  to  introduce  into 
the  circuit  more  length  of  car- 
bon than  is  strictly  necessary, 
even  if  its  resistance  diminishes 
when  heated. 

An  idea  of  the  factors  of  this 
problem  can  be  obtained  from 
the  following  figures,  resulting 
from  the  experiments  of  M. 
Joubert  with  Carre's  carbons : 


Diame- 
ters in 
millime- 

Eesistances 
in  ohms  at 
20°  centi- 

Equivalent length 
in  copper  wire  of 
four  millimetres 

tres. 

grade. 

diameter. 

1 

50-000 

20,000  metres. 

2 

12-500 

5,000       " 

3 

5-550 

2,222       " 

4 

3-125 

1,250       " 

5 

2-000 

800       " 

6 

1-390 

555       " 

Plain.  Copper-plated.      Nickel-plated. 

FIGS.  20,  21,  22. — Points  of  a  pair  of  car- 
bons, plain,  and  coated  with  metal. 


Between  32°  and  212°  the 
resistance  diminishes  ^V^  f°r 
each  degree  ;  at  1,832°  it  is  re- 
duced to  one  third. 

Gas-carbon  pencils  are  about 
seventy  times  more  resisting ;  those  of  M.  Gaudoin  would  be 
about  2 '16  times  more  resisting  than  those  of  M.  Carre. 

We  have  said  that  the  electric  light  is  principally  produced 
by  the  incandescence  of  polar  carbons,  and  that  it  is  the 
points  whence  the  current  flows  that  reach  the  highest  tern- 


54  THE  VOLTAIC  ARC. 

perature  ;  for  the  light  to  be  fixed,  these  points  must  displace 
themselves  as  little  as  possible  in  operation,  and  this  is  quite 
hard  to  realize  because  of  the  invincible  tendency  of  the  cur- 
rent to  choose  always  the  shortest  path — a  path  which  the 
wearing  away  of  the  carbons  is  continually  changing,  as  may 
be  seen  in  examining  the  image  of  a  voltaic  arc  magnified  and 
projected  on  a  screen.  The  displacement  of  the  points  of 
emission  is  one  of  the  principal  causes  of  the  oscillations  con- 
tinually objected  to  in  the  electric  light.  The  light  would 
unquestionably  be  more  fixed  and  more  intense  with  thinner 
carbons,  but  then  a  greater  part  of  their  length  would  grow 
red-hot,  and  would  be  burned  through  back  of  the  points  by 
slow  oxidation  by  the  air. 

To  prevent  this  waste  and  diminish  the  resistance  of  the 
carbons,  M.  Reynier  conceived,  in  1875,  the  idea  of  preventing 
the  contact  of  the  air  by  covering  the  carbons  with  a  metallic 
pellicle,  copper  or  nickel,  galvanically  deposited.  With  a  very 
thin  deposit  of  metal,  excellent  results  were  obtained.  M. 
Tchikoleff,  of  St.  Petersburg,  has  proved,  in  fact,  that  a  layer 
of  copper  ^-g-  millimetres  thick  increases  the  conductivity 
four  and  a  half  times  its  normal  amount ;  with  a  -^  coating, 
it  increases  one  hundred  and  eleven  times ;  the  duration  of  the 
carbon  can  be  at  the  same  time  increased  fourteen  per  cent, 
as  is  proved  by  experiments  made  by  M.  Lemonnier  with  a 
Gramme  machine  with  continuous  current  (Figs.  20,  21,  22) : 

Intensity  of 
the  lipht 
in  Carcels. 

947 
528 


Using  alternate  currents,  the  two  carbons  form  symmetrical 
points,  and  it  is  quite  easy  to  secure  steadiness.  With  con- 
tinuous currents  the  metallic  coating  does  not  become  dissi- 
pated quickly  enough  from  the  negative  carbon,  and  often 
forms  a  barricade  which  hides  part  of  the  light ;  the  best  plan 
is  to  employ  metallic  plating  only  for  the  positive  carbon. 

Trying  in  another  direction  to  secure  the  steadiness  of  the 
light,  M.  Carre  thought  of  constructing  the  polar  carbons  with 
a  very  fine  central  rod  of  carbon  inclosed  in  a  tube  of  carbon 


Diameter  of 
pencils  in                       Stat/  of 
millimetres.                    6urface' 
f  Plain  

Consumptio: 
Positive. 
166 

Q  per  hour  in  i 
Negative. 
68 

nillimetres. 
Total. 
234  \ 

7              •<  Copper-plated  .  . 
(  Nickel-plated  .  . 
(  Plain. 

146 
106 
104 

40 
38 
50 

186  [ 
144  ) 
154  i 

9              •<  Copper-plated.  . 
(Nickel-plated... 

98 
68 

34 
36 

/ 

132  [• 

104) 

SINGLE-LIGHT  REGULATORS.  55 

which  it  exactly  filled,  and  which  would  serve  to  support  it ; 
the  combustion  resembled  exactly  that  of  a  candle-wick  and 
the  wax  surrounding  it.  The  two  parts  of  the  carbon  natu- 
rally are  made  of  different  composition  appropriate  for  the 
different  roles  they  have  to  fill. 

By  using  these  carbons,  and  by  properly  reducing  the  sec- 
tion of  the  negative  carbon,  not  only  is  a  remarkable  steadi- 
ness attained,  but  the  peculiar  hissing  noise  that  too  often 
accompanies  the  voltaic  arc  is  suppressed,  a  hissing  that  must 
not  be  confounded  with  the  peculiar  rustling  inseparable  from 
the  employment  of  alternating  currents,  but  which  does  not 
exist  when  continuous  currents  are  employed. 


CHAPTER  IV. 

SINGLE-LIGHT  REGULATORS. 

THE  electric  lamp  for  production  of  the  voltaic  arc  is  com- 
posed essentially  of  two  rods  of  carbon,  shaped  at  the  ends 
like  pencils,  and  placed  in  the  prolongation  of  their  mutual 
axis ;  between  these  electrodes  the  current  passes,  and  forms 
the  voltaic  arc.  We  have  already  explained,  in  the  preced- 
ing chapter,  the  nature  of  the  carbons  employed,  and  the 
cause  of  the  brilliant  light  produced.  It  remains  to  be  shown 
how  this  light  can  continue  long  enough  and  in  a  sufficiently 
regular  manner  to  constitute  a  practical  system. 

When  the  current  is  to  be  made  to  pass  from  one  of  the 
carbons  to  the  other — that  is  to  say,  when  the  lamp  is  to  be 
lighted — the  carbons  must  be  put  in  contact,  end  to  end,  be- 
cause the  electric  current  is  incapable  of  overcoming  the  re- 
sistance which  the  almost  non-conductivity  of  cold  air  offers 
to  its  passage.  The  ends  of  the  carbon-rods,  sharpened  to  a 
point,  soon  grow  red,  because  of  the  crowding  of  the  electric 
molecules  in  this  choked  passage.  The  air  becomes  heated 
by  these  incandescent  points,  and  thus  becomes  capable  of 
conducting  a  little  electricity.  The  carbon-rods  must  then 
be  separated  from  each  other  a  certain  distance,  to  cause  the 
development  of  the  voltaic  arc  in  all  its  powerful  brilliancy. 

We  now  have  the  lamp  lighted.     Unfortunately,  it  threat- 


56 


THE   VOLTAIC   ARC. 


ens  to  go  out  very  soon.  In  fact,  the  carbon,  brought  to  in- 
candescence, burns  quite  rapidly,  however  compact  it  may 
be.  The  rods,  or  electrodes,  continually  grow  short,  so  that 
the  distance  which  the  electricity  has  to  traverse  in  air  aug- 
ments every  moment.  As  air  even  when  heated  is  a  poor 
conductor,  the  current  experiences  an  increasing  resistance 
before  it,  which  it  soon  is  unable  to  overcome.  Then  the 
voltaic  arc  disappears,  and  the  lamp  goes  out. 

To  add  to  the  trouble,  the  two  carbons  burn  unevenly  be- 
cause of  the  difference  of  their  physical  condition,  and  be- 
cause of  the  transportation  of  particles  of  incandescent  car- 
bon from  one  pole  to  the  other 
under  the  effect  of  the  current. 
The  positive  pole  burns  twice 
as  rapidly  as  the  negative  one, 
which  is  the  cause  of  several-  in- 
conveniences. Thus,  the  center 
of  radiation,  which  evidently  cor- 
responds to  the  center  of  the  vol- 
taic arc,  or  center  of  the  inter- 
val between  the  two  electrodes, 
is  displaced  by  receding  from 
the  positive  pole.  Furthermore, 
the  poles  themselves  change  their 
form,  and  do  not  any  longer  re- 
semble each  other  in  shape  (see 
ante,  Fig.  15,  page  33,  and  Figs. 
20-22,  page  53). 

While  the  negative  pole  grows 
more  pointed,  the  positive  pole 
hollows  out  into  the  shape  of  a 
little  crucible,  facing  the  oppo- 
is  called  the  crater.  The  light 
becomes  brighter  there  than  in  other  parts  of  the  voltaic 
arc,  which  increases  still  further  the  variations  in  light  pro- 
duced by  the  other  causes.  From  an  early  period,  when 
this  light  was  only  employed  for  scientific  projections,  M. 
Duboscq  had  shown  that  the  defect  could  be  partly  cured,  and 
more  light  could  be  obtained  by  placing  one  carbon,  the  nega- 
tive one,  a  little  in  front  of  the  other  (Fig.  23).  This  artifice 
is  employed  at  the  present  day  in  the  powerful  lights  of  light- 
houses, where  continuous  currents  are  employed.  MM.  Fon- 


FIG.  23. — One-sided  position  of  the  car- 
bons, for  the  purpose  of  causing  the 
light  to  be  of  greater  intensity  in  one 
direction. 

site   carbon.     This   hollow 


SINGLE-LIGHT  REGULATORS. 


57 


taine  and  Lemonnier  in  France,  and  Messrs.  Tyndall  and 
Douglass  in  England,  have  made  many  experiments  on  this 
subject,  which  prove  that  the  intensity  is  thus  increased  fifty 
per  cent  in  the  line  in  which  the  radiation  is  directed. 

But,  for  most  applications,  it  is  necessary  above  all  to  have 
an  equal  distribution  of  light,  so  that  anything  which  tends 
to  diminish  it  becomes  a  grave  fault,  which  fault  is  avoided 
where  alternating  currents  are  employed. 

If  the  lamp  after  being  lighted  is  left  to  itself,  it  begins  to 
burn  for  some  minutes  with  a  very  variable  intensity,  then  it 
suddenly  grows  weak  and  goes  out.  To  prevent  this  extinc- 
tion from  taking  place,  the  carbons  must  be  continually 
brought  together,  so  that  their  distance  apart  shall  remain 
substantially  the  same.  The  ideal  would  be  to  cause  them  to 
advance  both  together  with  a  continuous  and  regular  move- 
ment in  exact  proportion  to  their  consumption.  This  is  the 


FIG.  24. — Carbon-holder  regulated  by  hand, 
for  the  production  of  the  electric  light. 


FIG.  25.— Primitive  carbon-holder,  for  pro- 
duction of  the  electric  light  in  a  vacuum. 


principal  trouble  with  electric  lamps  ;  it  is  on  this  point  that 
almost  all  inventors  have  concentrated  their  efforts,  and  it  is 
in  this  particular  that  most  electric  lights  differ,  except  the 
incandescent  systems,  which  solve  the  problem  in  another 
way. 

At  first,  the  operation  was  conducted  by  hand.     The  car- 
bons were  fixed  to  metallic  rods,  one  of  which  worked  by 


58 


THE  VOLTAIC   ARC. 


friction  in  a  fixed  ring.  The  movement  was  by  the  hand  of 
the  operator :  the  movable  rod  was  pushed  down  to  light  the 
lamp,  it  was  drawn  up  a  little  to  extend  the  arc,  then  from 
time  to  time  it  was  slightly  advanced  as  the  brightness  of  the 
arc  diminished  sufficiently  to  call  attention  to  it.  As  it  was 
necessary  to  be  very  close  to  the  lamp  in  working  this  rod, 
there  is  no  need  of  mentioning  the  dangers  encountered  by 
the  eyes  of  the  unfortunate  being  in  charge  of  this  work  (Figs. 
24  and  25).  It  was  thus  that  Sir  Humphry  Davy  operated  in 
1813,  sometimes  in  the  open  air,  sometimes 
in  a  vacuum.  Imperfect  as  this  method 
was,  it  was  thus  that  thirty  years  later  Leon 
Foucault  worked  in  his  first  researches,  and 
that  Deleuil,  in  his  public  experiments  in 
lighting  in  Paris,  operated  on  the  Place  de 
la  Concorde  and  in  front  of  La  Monnaie. 

This  process,  crude  in  a  double  sense, 
which  we  have  all  of  us  seen  followed  in 
experiments  in  courses  of  physics,  governs 
the  light,  as  is  evident,  in  a  very  imperfect 
manner  by  fits  and  starts.  It  is  seldom 
employed  now  even  for  the  use  of  labora- 

C,  lower  carbon. 

E',  rack  by  which  it  was  raised  or  lowered  by  aid  of  the  pinion  P. 

C',  upper  carbon. 

0,  guide,  which  can  be  displaced  at  pleasure.  When  there  is 
used,  as  shown  in  the  figure,  a  long  and  thin  rod  of  carbon, 
whose  resistance  is  great,  the  guide  is  placed  on  the  bar  E. 
It  supports  the  carbon  and  facilitates  the  passage  of  the  cur- 
rent, and  limits  the  length  of  the  incandescent  portion. 

E,  rack  worked  by  the  pinion  P'  for  the  upper  carbon-holder. 

B,  B',  buttons  for  bringing  the  point  of  the  upper  carbon  into 
position. 

r,  r',  contact  springs. 

B",  button  for  holding  the  upper  carbon. 

P".  button  for  working  the  third  rack,  serving  to  raise  or  lower 
the  luminous  center. 

S,  foot  of  the  lamp. 


FIG.  26.— Hand-regulator 
of  M.  Boudreaux,  with 
vertical  carbon-hold- 
ers, for  magic  lanterns 
and  other  experiments 
with  electric  light. 


tories.     It  is  almost  everywhere  replaced  by  the  hand-regu- 
lator of  M.  Boudreaux  (Fig.  26),  which  works  much  better. 

If,  for  so  many  years,  no  better  method  was  sought  for,  it 
is  because  the  light  was  as  yet  but  a  simple  curiosity  of  the 
laboratory,  and  a  curiosity  rarely  exhibited  because  of  its 
great  expense,  and  of  the  endless  variety  of  trouble  entailed 
in  its  preparation.  The  batteries  then  at  the  disposal  of  the 


SIT 


SINGLE-LIGHT  REGULATORS. 

physicist  were  very  weak,  so  that  it  was  necessary 
multitude  of  elements  to  obtain  the  strong  currents  necessary 
for  the  electric  light.  Sir  Humphry  Davy,  as  has  been  seen, 
never  employed  less  than  two  thousand.  Even  in  the  best 
laboratories  this  involved  an  expense  and  trouble  that  no  one 
would  dream  of  encountering  to-day. 

The  discovery  of  the  Bunsen  battery,  which  was  published 
in  1840,  changed  the  state  of  affairs  by  placing  at  the  disposal 
of  all  a  battery  much  more  powerful,  and  relatively  less  cum- 
brous, and  at  the  same  time  less  costly.  Thus  it  is  since  the 
year  1844  that  the  electric  light 
has  been  seriously  studied,  and 
all  at  once  a  means  of  regulating 
it  was  searched  for  that  would 
effect  mechanically  the  approach 
of  the  carbons. 

The  first  trial  which  gave  any 
results  dates  from  1845.  It  is  due 
to  an  Englishman  named  Thomas 
Wright,  who  conceived  the  idea 
of  replacing  the  cylindrical  car- 
bon-rods by  disks  beveled  on 
their  peripheries,  and  turned  by 
a  special  mechanism,  which  kept 
them  at  a  constant  distance.  The 
voltaic  arc  played  between  these 
disks.  The  attempt  of  Thomas 
Wright  passed  almost  without 
notice ;  and  almost  the  same  may 
be  said  of  an  analogous  experi- 
ment of  a  French  physicist,  Le 
Molt,  known  also  by  his  experi- 
ments on  artificial  carbons.  He 
patented  in  1849  an  apparatus 
capable  of  acting  automatically, 


FIG.  27.— Harrison's  regulator  (1857). 
The  lower  carbon  consists  of  a  disk 
rotating  on  its  axis.  The  upper  car- 
bon is  kept  at  a  suitable  distance  by  a 
cord  running  over  pulleys,  and  gov- 
erned by  the  armature  of  an  electro- 
magnet placed  below. 


according  to  his  accounts,  for  twenty  or  thirty  hours,  without 
the  need  of  any  intervention  by  the  hand  of  the  operator. 
Nevertheless,  the  idea  was  taken  up  later  (1857),  with  some 
modifications,  by  Mr.  Harrison  (Fig.  27)  ;  and  the  recent 
apparatus  of  M.  Reynier  presents  many  analogies  with  this 
system,  originally  unsuccessful. 

But  two  or  three  years  later,  about  1848,  Messrs.  Staite 


60  THE  VOLTAIC  APwC. 

and  Petrie  in  England,  and  Leon  Foucanlt  in  France,  worked 
afc  the  same  problem  in  an  altogether  different  way. 

To  them  is  due  the  first  serious  solution — even  if  as  yet  it 
is  not  practical  in  all  its  details — of  this  difficult  problem, 
and  it  is  in  the  road  opened  up  by  their  labors  that  inventors 
are  now  marching. 

I.  KEGULATORS  WITH  ELECTRO-MAGNETS. 

How  may  the  problem  be  summed  up  ?  The  burning  up 
of  the  carbons  under  the  effect  of  the  heat  increases  the  dis- 
tance between  them,  and  for  a  continuous  light  they  must  be 
brought  together ;  but  this  must  be  done  at  the  proper  mo- 
ment. Suppose  it  is  done  too  soon,  the  voltaic  arc  is  short- 
ened until  it  disappears  ;  if  done  too  late,  on  the  contrary,  it 
grows  weaker,  and  perhaps  is  extinguished.  How,  then,  can 
the  exact  moment  of  action  be  chosen? 

No  one  can  know  this  exact  moment  or  feel  it  better  than 
does  the  current  itself.  If  the  distance  of  the  carbons  in- 
creases, the  current  has  more  difficulty  in  traversing  the 
elongated  aerial  conductor;  if,  on  the  other  hand,  the  dis- 
tance diminishes  too  much,  the  current  knows  it  very  well, 
for  then  it  passes  more  readily.  Like  a  well-trained  sentinel, 
it  is  not  satisfied  to  remark  the  occurrence,  it  wishes  to  notify 
us  of  it ;  for,  in  the  first  case,  its  intensity  becomes  less  on 
account  of  the  greater  resistance  it  encounters,  and  in  the 
second  case,  on  the  contrary,  its  intensity  increases  from  the 
reciprocal  cause. 

All  this  can  easily  be  proved  with  a  galvanometer,  but 
that  is  not  enough.  After  having  been  notified  by  the  cur- 
rent itself,  the  same  current  must  be  made  to  work,  and  by 
its  own  efforts  prevent  the  evil  it  has  been  demonstrating. 
This  is  achieved  by  forcing  the  current  to  pass,  before  going 
to  the  carbons,  through  the  magnetizing  helix  of  an  electro- 
magnet, whose  armature  has  the  office  of  regulating  the  move- 
ments of  the  mechanism  which  advances  the  carbons. 

The  strength  of  this  electro -magnet  varies  with  the  inten- 
sity of  the  current,  and  the  armature  is  in  turn  attracted 
and  released  at  the  precise  moments  where  its  intervention 
is  necessary  to  regulate  the  approach  of  the  carbons. 

This  is  the  very  simple  principle  upon  which  the  regulator 
of  Foucault  works,  so  simple  that  one  asks  why  it  was  not  at 


SINGLE-LIGHT  REGULATORS.  61 

once  thought  of  as  soon  as  the  researches  of  Oersted  and  Am- 
pere had  revealed  the  laws  of  electro-magnetism.  But,  if 
attention  was  not  earlier  turned  in  this  direction— in  other 
words,  before  1847,  the  date  of  the  first  labors  of  Foucault — 
the  art  of  making  small,  easily-worked  electro-magnets  was 
not  known.  For  it  would  not  do  to  introduce  into  these  deli- 
cate pieces  of  apparatus  parts  weighing  a  quintal  or  half  a 
quintal,  like  those  hitherto  employed.  It  is  thus  that  all 
scientific  progress  advances,  and  it  often  happens  that  very 
slight  improvements  in  a  given  point  of  construction,  even  in 
a  secondary  one,  carry  with  them  a  considerable  progress  in  a 
number  of  other  more  important  points. 

This  has  all  happened  with  the  regulator  of  Foucault, 
whose  mechanical  complication  was  in  other  respects  very 
great.  Thus  he  himself  describes  it  in  a  summary  manner : 
"  The  two  carbon-holders  are  pressed  together  by  springs; 
but  they  can  not  come  in  contact  without  moving  a  train  of 
wheels,  the  last  of  which  is  controlled  by  a  detent.  It  is  here 
that  electro-magnetism  is  used.  The  current  which  causes  the 
illumination  passes  through  the  spirals  of  an  electro-magnet, 
whose  energy  varies  with  the  intensity  of  the  current ;  this 
electro-magnet  acts  upon  an  armature  of  soft  iron,  drawn 
away  from  it  again  by  a  counteracting  spring.  Upon  this 
movable  armature  is  fastened  the  detent  which  locks  the  train 
or  releases  it  as  the  current  dictates,  and  the  motion  of  the 
detent  is  such  that  it  presses  upon  the  wheel  when  the  cur- 
rent grows  strong,  or  lets  it  go  when  the  current  grows  weak. 
Now,  just  as  the  current  grows  strong  or  weakens,  as  the  inter- 
polar  distance  diminishes  or  increases,  it  will  be  understood 
that  the  carbons  have  the  liberty  of  approaching  at  the  mo- 
ment when  the  distance  between  them  tends  to  increase,  and 
that  this  approaching  can  not  bring  them  in  contact,  because 
the  increased  electro-magnetic  action  resulting  therefrom  of- 
fers an  insurmountable  obstacle,  which  disappears  of  its  own 
accord  as  the  interpolar  distance  again  increases." 

It  appears,  then,  that  the  motion  of  the  carbon  in  this 
apparatus  is  intermittent ;  but,  as  the  periods  of  repose  and 
advancing  should  follow  each  other  with  great  rapidity,  and 
last  but  a  short  space  of  time  for  each  one,  Foucault  supposed 
that  this  in  practice  would  amount  to  the  continuous  move- 
ment of  progression  necessary  for  the  fixity  of  the  light. 

Nevertheless,  the  regulator  had  more  than  one  fault,  and 


62 


THE  VOLTAIC  ARC. 


FIG.  28.— First  regulator  of  the  electric  light  of  Foucault  (1849;. 

c,  positive  carbon-holder  car.    c\  negative  carbon-holder  car. 

R,  R',  springs  which  push  the  cars  together  and  conduct  the  current. 

L,  large  lever  which  forces  the  cars  to  move  simultaneously,  causing,  by  the  attachment  of 
the  return  cord  p',  p" ',  p'"  to  the  lever,  the  car  c'  to  move  slower  than  the  other. 

T,  little  windlass,  serving  to  regulate  the  position  of  car  c'. 

M,  clock-work,  to  which  the  car  c  is  attached  by  the  cord  jo,  and  whose  scape-wheel,  held 
by  a  detent,  can  not  move. 

E,  electro-magnet  with  thick  wire,  through  which  the  current  passes. 

A,  armature  of  the  electro-magnet,  pivoted  at  r'  to  a  Robert  Houdin  lever. 

D,  rod  of  the  detent  mounted  on  the  armature.  When  the  current  grows  strong,  the  armature 
is  drawn  down,  the  detent  presses  upon  the  wheel,  and  the  cars  cease  to  move.  When 
the  current  grows  weak,  the  detent  releases  the  wheel,  and  the  cars  approach  each  other. 

r,  counteracting  spring  drawing  back  the  armature,    d,  hand-lever  for  stopping. 

K,  regulator  of  the  current,  whose  use  is  rendered  necessary  by  the  battery  which  produces 
the  electricity ;  it  is  made  of  two  plates  of  platinum,  arranged  parallel  to  each  other,  one 
millimetre  apart,  and  insulated  from  one  another.  The  current  passes  from  one  to  the 
other  through  the  conducting  fluid  (sulphate  of  potash  solution),  into  which  they  are 
plunged  to  a  greater  or  less  depth  in  proportion  to  the  intensity  of  the  current. 


SINGLE-LIGHT  KEGULATORS. 


63 


was  not  entirely  automatic,  because  it  required  the  aid  of  an 
operator's  hand  to  light  the  lamp  at  the  beginning  by  sepa- 
rating the  carbons.  Foucault  was  obliged  to  further  compli- 
cate it  to  overcome  this  imperfection. 

The  new  machine  had  two  distinct  clock-movements — one 
to  bring  the  carbons  together,  the  other  to  separate  them. 
An  electro -magnet  placed  in  the  circuit  unlocked  and  put  one 
or  the  other  of  these  movements  into  action  by  means  of  a 
lever  fastened  to  its  armature.  This  is 
attracted  in  one  direction  by  an  electro- 
magnet, and  in  another  by  an  opposing 
spring,  whose  tension  is  regulated  in  pro- 
portion to  the  intensity  of  the  current 
employed.  The  inconvenience  of  such  a 
spring,  which  the  variations  of  the  cur- 
rent can  not  influence,  and  which  has  to 
be  adjusted  by  hand  in  proportion  to  the 
power  of  the  electro-magnet  opposed  to 
it,  can  be  easily  understood. 

M.  Duboscq,  who  had  been  the  collab- 
orator of  Foucault,  introduced  several 
other  improvements  in  this  apparatus 
(Fig.  29),  which  is  used  in  this  form  in 
all  laboratories,  and  at  all  the  lectures 
in  which  M.  Duboscq  so  often  gives  his 
assistance. 

It  is  also  with  this  regulator  that  he 
has  introduced  the  electric  light  into  the 
opera,  and  it  is  always  it  that  is  used 
when  it  is  necessary  to  introduce  the  sun 
upon  the  scene,  as  when  grand  effects  of 
light  should  mingle  with  the  expressive 
dances  of  the  ballet. 

These  two  regulators  of  Foucault  and  Duboscq  have  served 
as  types  for  their  followers,  which  differ  from  them  in  the 
most  diverse  mechanical  combinations,  but  which  resemble 
them  in  their  physical  principles.  We  will  only  examine 
those  more  widely  used ;  but  many  others  exist  which  pre- 
sent almost  analogous  arrangements. 

In  the  year  1859  M.  Serrin  constructed  a  regulator  realiz- 
ing the  different  conditions  of  the  problem  by  new  and  very 
ingenious  arrangements.  The  clock-work  is  done  away  with, 


FIG.   29.—  Regulator  of  J. 
Duboscq. 


64 


THE  VOLTAIC   ARC. 


FIG.  30.— Serrin's  regulator  (1859). 


H,  upper  carbon-holder  (positive). 

J,  movable  intervening  piece,  which  is 
advanced  or  drawn  back  by  means 
of  the  button  S. 

G,  button  terminating  in  a  small  eccen- 
tric. The  two  buttons,  S  and  G,  per- 
mit the  upper  carbon  to  be  moved 
in  two  directions,  to  keep  the  points 
well  opposed  to  ench  other. 

B,  stationary  tube  serving  as  guide  to 
the  rod  of  the  upper  carbon-holder. 
This  rod  is  provided  with  a  rack  on 
its  lower  end,  and  serves  by  its  weight 
as  motor  for  the  whole  apparatus. 

C,  lower  carbon-holder  (negative). 

M,  N,  P,  Q,  jointed  parallelogram,  or 
oscillating  system,  serving  to  gov- 
ern the  advance  of  the  carbons. 

0,  series  of  cog-wheels,  the  first  of  which 
engages  with  the  rack  of  the  upper 
carbon-holder,  and  transmits  the 
movement  to  the  lower  carbon-hold- 
er by  means  of  a  small  fusee-chain, 
whose  extremity  is  fastened  to  the 
stud  F.  The  last  axle  carries  a 
rachct,  on  which  acts  an  abutment 
fixed  on  one  of  the  sides  of  the  par- 
allelogram. 

E,  springs :  one  is  fixed,  and  balances 
the  weight  of  the  movable  pieces 
fastened  to  the  oscillating  system ; 
the  other  serves  as  opposing  spring 
against  the  action  of  the  electro- 
magnet on  its  armature. 

D,  armature  of  soft  iron  fixed  to  the 
oscillating  system.   A,  electro-mag- 
net. 

K,  L,  lever  regulating  the  tension  of  the 
opposing  spring.  If  the  electric  cur- 
rent does  not  circulate,  the  electro- 
magnet is  inactive ;  the  oscillating 
system  is  kept  up  by  the  springs; 
the  rachet  is  free,  and,  under  the  in- 
fluence of  the  weight  of  the  upper 
carbon-holder,  the  wheels  turn  and 
the  carbons  approach  each  other. 
If  the  current  is  now  turned  on,  it 
passes  through  the  rod  B II,  through 
the  carbons  which  arc  in  contact, 
descends  the  rod  C,  and,  by  the  in- 
termediation of  the  corrugated  plate 
which  is  seen  behind,  reaches  the 
electro-magnet,  and  returns  to  the 
generator.  The  electro -magnet,  put 
into  motion  by  this  passage  of  the 
current  through  its  helices,  attracts 
its  armature  ;  the  oscillating  system 
drops  down,  the  lower  carbon  de- 


SINGLE-LIGHT  REGULATORS. 


65 


scends,  the  stop-piece  catches  in  the  rachet,  the  wheel-work  becomes  motionless,  and  the 
descent  of  the  upper  carbon  is  arrested.  The  two  carbons  separate,  and  the  arc  is  started. 
Each  time  that  the  increased  length  of  the  arc  weakens  the  current,  the  electro-magnet 
releases  its  armature,  and  the  same  movements  of  approach  and  then  of  separation  are 
repeated. 

and  the  carbons  are  advanced  simply  by  the  weight  of  the 
upper  carbon-holder.  The  rod  of  the  lower  carbon-holder 
is  carried  by  an  oscillating  parallelogram  sustained  by  two 
springs,  one  of  which  is  fixed,  and  keeps  an  equilibrium  be- 
tween the  weights  of  the  movable  pieces,  while  the  other  is 
governed  by  hand  by  means  of  a  button  (Fig.  30). 

An  electro-magnet,  worked  by  the  current  of  the  lamp, 
also  governs  the  movement  of  the  apparatus ;  but  its  arma- 
ture, fastened  to  the  oscillating 
parallelogram,  fills  a  double 
role :  at  the  time  it  stops  at  the 
proper  moment  the  approach 
of  the  carbons,  by  acting  on  a 
rachet- wheel,  it  causes  the  for- 
mation of  a  voltaic  arc  by  at- 
tracting the  lower  carbon-hold- 
er, and  producing  thus  between 
the  points  of  carbon  the  neces- 
sary distance,  so  that  the  lamp 
lights  of  its  own  accord  when 
it  receives  the  current.  It  is 
the  second  spring  that  has  to 
furnish  the  force  necessary  to 
draw  back  this  armature  of  the 
electro-magnet  when  the  latter 
is  weakened  through  diminu- 
tion of  the  strength  of  the  cur- 
rent. 

On  account  of  the  exactness 
of  its  movements  the  carbons 
progress  with  absolute  steadi- 
ness and  regularity.  It  is  the 
apparatus  adopted  since  1863 
for  light-house  illumination  in 
France  and  England ;  it  has 

been  for  a  long  time  the  principal  reliance  of  electricians,  and 
has  contributed  largely  to  the  success  of  electric  lighting. 

In  the  Burgin  lamp,  now  antiquated,  the  movement  of  the 


FIG.  31.—  Burgin' s  regulator. 


66  THE  VOLTAIC  ARC. 

moving  carbon  (or  of  both  carbons  in  another  model)  is  gov- 
erned by  a  spring-brake,  only  it  is  not  the  brake  which  is 
displaced,  but  the  fly-wheel  on  which  it  acts.  This  wheel  is 
fastened  to  the  armature  of  an  electro-magnet  with  thick 
wire,  and  moves  with  it.  When  the  current  passes  with  full 
energy  the  armature  is  attracted  ;  the  wheel  is  raised  up,  and 
presses  upon  the  brake,  which  stops  it  from  turning.  When 
the  current  begins  to  grow  weak,  the  armature  and  wheel  fall 
down,  and  the  carbon  can  descend.  The  slight  displacement 
of  the  armature  is  transmitted  to  the  lower  carbon  by  a  cord, 
and  suffices  to  produce  the  separation.  This  apparatus  (Fig. 
31)  is  arranged  for  only  one  light,  but  it  can  easily  be  changed 
so  as  to  act  for  several  luminous  centers,  according  to  princi- 
ples which  will  be  explained  in  the  next  chapter. 

The  Gulcher  lamp  is  also  a  single-light  lamp  of  great  sim- 
plicity. The  rod  of  the  upper  carbon-holder  is  of  iron,  its 
descent  is  regulated  by  the  attraction  of  a  straight  electro- 
magnet, mounted  on  trunnions  like  a  cannon,  and  which  oscil- 
lates perpendicularly  before  it.  The  farther  end  of  this  elec- 
tro-magnet is  placed  iinder  a  block  of  iron,  which  attracts  and 
balances  it.  The  other  end  raises  the  rod  of  the  positive  car- 
bon and  produces  the  separation.  The  reverse  takes  place 
every  time  the  current  weakens.  The  two  carbon-holders  are 
united  by  a  connecting  cord,  and  their  movements  are  coin- 
cident. 

Finally,  the  lamp  of  M.  Girouard  must  be  cited,  invented 
in  the  beginning  of  1876,  because  it  shows  a  disposition  of 
parts  which  is  peculiar  to  it.  The  apparatus  is  divided  into 
two  distinct  parts :  one  the  lamp,  properly  so  called,  with 
clock-work  for  approaching  and  separating  the  carbons  ;  and, 
second,  the  regulator  in  the  form  of  a  relay,  which  can  be 
placed  at  a  distance  from  the  lamp,  and  which  works  by 
means  of  a  small  special  battery. 

In  this  apparatus,  then,  there  are  two  distinct  currents. 
The  first,  which  comes  from  the  dynamo-electric  machine,  is 
very  intense,  and  serves  for  the  production  of  the  electric 
light,  having,  however,  first  passed  through  the  bobbin  of  an 
electro-magnet  fixed  to  the  relay.  The  second  current,  which 
comes  from  the  battery,  is  very  feeble,  and  has  nothing  to  do 
but  to  start  the  clock-work,  which  advances  or  draws  back 
the  carbons.  A  very  complicated  mechanism  permits  the 
electro-magnet  of  the  relay  to  act  upon  the  lamp.  This  sys- 


SINGLE-LIGHT    REGULATORS. 


tern  has  only  one  advantage  :  that  it  permits  the  operator  to 
govern  from  a  distance  the  movements  of  the  apparatus,  some- 
thing that  in  many  cases  is  very  convenient. 


II.   SOLENOID  REGULATORS. 

While  Foucault  worked  at  his  regulator,  founded  on  the 
action  of  electro-magnets,  another  French  savant,  Archereau, 
invented  an  apparatus  founded  on  the  action  of  solenoids, 
and  which,  differing  from  that  of  Foucault,  is  distinguished 
by  great  simplicity. 

A  solenoid  is  a  spiral,  or  helix — a  sort  of  corkscrew,  if 
you  please — through  which  a  current  passes.  When  an  iron 
rod  is  passed  through  the  opening  in  a  solenoid,  as  if  in  a 
sheath,  its  tendency  is  to  place 
itself  symmetrically  with  respect 
to  the  two  ends  of  the  solenoid  ; 
consequently  it  is  attracted  by  it, 
and  that  with  more  or  less  force 
according  as  the  current  passing 
through  the  solenoid  is  of  greater 
or  less  intensity.  This  is  the  prin- 
ciple of  Archereau' s  regulator. 

In  this  apparatus  the  positive 
carbon  placed  above  is  station- 
ary. As  for  the  negative  carbon, 
placed  below,  it  is  attached  to  a 
rod  of  iron,  situated  in  the  mid- 
dle of  the  solenoid,  and  balanced 
by  a  counterpoise  by  means  of  a 
cord  passing  over  a  pulley.  The 
current  of  the  voltaic  arc  passes 
through  the  solenoid  wire,  and  it 
is  at  once  clear  that  its  variations 
will  bring  about  the  rise  or  fall  of  the  negative  carbon  at  the 
right  time  if  all  the  parts  of  the  apparatus  are  properly  pro- 
portioned. 

Archereau' s  regulator  has  no  clock-work.  It  is  a  true  mar- 
vel of  simplicity  ;  so  much  so,  that  the  first  model  constructed 
only  cost  seventeen  francs,  and,  notwithstanding,  does  actually 
work,  if  not  always  perfectly.  But,  as  it  is  not  the  positive 
carbon  that  moves,  the  negative  carbon  must  rise  to  follow  its 


FIG.  32. — Archereau' s  regulator,  type  of 
solenoid  regulators. 


68 


THE  VOLTAIC  ARC. 


H,  H',  carbon-holders,  upper  and  lower. 

I,  rod  of  the  carbon-holder  H,  provided 
at  its  lower  extremity  with  a  rack. 

K,  rod  of  the  lower  carbon-holder ;  it  is 
of  soft  iron  and  of  quadrangular  sec- 
tion. The  upper  part  is  provided 
with  a  rack;  the  lower  enters  into 
the  interior  of  the  bobbin  L. 

M,  M',  cog-wheels  turning  freely  on  the 
axle  W,  and  separated  one  from  the 
other  by  an  ivory  wheel ;  their  diam- 
eters arc  in  the  ratio  of  1  to  2.  The 
larger  engages  "with  the  rod  I,  and 
the  smaller  with  the  rod  K.  The 
distances  traversed  by  these  rods  are 
thus  proportional  to  the  consumption 
of  the  carbons. 

O,  barrel  containing  a  spring  which  tends 
constantly  to  bring  the  rods  together, 
and,  consequently,  the  carbons. 

W,  extremity  of  the  arbor,  terminated 
by  a  square  shank  for  receiving  the 
key  with  which  the  tension  of  the 
spring  is  adjusted. 

E,  K',  R",  reverse  motion-pinions.  They 
can  be  displaced  in  parallelism  with 
themselves,  and  act  upon  the  rods  I 
and  K  when  both  carbons  are  to  be 
raised  or  lowered  without  stopping 
the  working  of  the  apparatus.  The 
axle  of  these  pinions  carries  for  this 
purpose  a  square  shank  to  receive  a 
key.  A  spring  placed  on  the  same 
axle  takes  them  out  of  engagement 
when  the  key  is  no  longer  turned. 
L,  hoilow  electro-magnetic  bobbin, 
whose  helix  increases  in  thickness 
from  top  to  bottom. 

X,  vertical  rod  for  the  passage  of  the 
current  from  the  binding-screw  P  to 
the  column  J. 

Y,  contact-key,  penetrating  by  an  open- 
ing through  the  tube  J,  and  bearing 
against  the  rod  I  by  a  spring,  to  in- 
sure the  contact  necessary  for  the 
passage  of  the  current. 

U,  guides  serving  to  direct  the  rods  I  and 
K,  and  prevent  them  from  turning. 
As  long  as  the  current  does  not  pass, 
the  carbons  arc  kept  in  contact  by 
the  barrel  and  spring ;  but,  as  soon 
as  it  is  passed  into  the  apparatus,  the 
bobbin  attracts  the  rod  K,  and,  as  the 
two  rods  are  connected,  the  carbons 
FIG.  33. — Gaiffers  regulator.  separate,  and  the  arc  is  established. 

Its  length  is  regulated  by  the  tension 

of  the  spring,  which  should  be  in  equilibrium  with  the  attractive  force  of  the  bobbin. 
While  the  increased  length  of  the  arc  diminishes  the  force  of  contact,  the  spring  overcomes 
the  attraction  of  the  bobbin,  and  the  carbons  approach  until  equilibrium  is  re-established. 


SINGLE-LIGHT  REGULATORS. 


waste,  so  that  the  lumi- 
nous center  is  continual- 
ly shifting,  in  the  exact 
ratio  that  the  positive 
carbon  burns  away — an 
inconvenience  that  does 
not  exist  in  the  Foucault 
regulator. 

As  derivatives  of  the 

A,  rod  of  positive  carbon-holder.     A 
guide,  placed  at  the  lower  part  of 
this  rod,  prevents  it  from  turning, 
and  keeps  the  carbons  opposite  one 
another. 

B,  iron  rod  of  the  negative  carbon- 
holder.   These  two  rods  are  united 
by  two  small  cords  to  the  rim  of 
two  pulleys,  which  work  together, 
and  of  which  one  has  twice  the 
diameter  of  the  other,  so  that  the 
rod  A  descends  twice  as  fast  as 
the  rod  B  rises. 

C,  solenoid  with  coarse  wire,  through 
whose  interior  the  rod  B  descends. 

D,  small  cylinder  filled  with  mercury. 
L,  stem  fastened  to  the  rod  B,  and 

ending  below  in  a  little  piston, 
which  plunges  into  the  cylinder 
D,  but  with  enough  clearance  for 
the  mercury  to  pass  it. 

F,  counter-weight  sliding  on  a  hori- 
zontal lever,  fastened  by  a  cord  to 
a  third  pulley,  which  works  in 
unison  with  the  other  two.  It  acts 
in  the  opposite  direction  to  the 
motor  rod  A. 

K,  button  by  which  the  weight  F  is 
brought  nearer,  or  pushed  away, 
according  as  it  is  desirable  to  aug- 
ment or  diminish  its  action,  and 
regulate  thus  the  quickness  of  pro- 
gression of  the  carbons  according 
to  the  intensity  of  the  current. 

E,  counterpoise  fastened  between  the 
arms  of  the  first  pulley,  and  serv- 
ing to  balance  the  variations  in 
the  attraction  of  the  solenoid  on 
the  rod  B.    As  the  pulley  turns, 
the  action  of  the  weight  dimin- 
ishes at  the  same  time  that  the  at- 
traction of  the  solenoid  diminish- 
es, by  the  deeper  penetration  of  the 
rodB. 


FIG.  34. — Jaspar'a  regulator. 


70 


THE   VOLTAIC  ARC. 


I 


Archereau  type,  the  regulators  of  MM.  Gaiffe  and  Jaspar 
must  be  cited.  In  the  regulator  of  M.  Gaiffe  the  motor  is  a 
spring  inclosed  in  a  barrel.  This  spring  is  wound  up  by  the 
same  movement  of  separation  of  the  carbon-holders  that  is 

needed  to  put  the  carbons  in 
place,  and  in  position  for  act- 
ing. The  solenoid  is  formed 
by  a  helix  whose  turns  increase 
from  top  to  bottom,  so  that  a 
stronger  and  stronger  attrac- 
tion is  continually  exerted  on 
the  iron  rod  which  terminates 
the  lower  carbon-holder.  Thus 
the  necessary  length  of  move- 
ment is  obtained  (Fig.  33). 

This  apparatus  is  supplied 
with  an  arrangement  which 
permits  the  two  carbons  to  be 
raised  or  lowered  at  will  and 
simultaneously,  without  extin- 
guishing the  arc.  This  condi- 
tion is  indispensable  when  the 
luminous  center  has  to  be  kept 
in  the  focus  of  optical  appa- 
ratus, such  as  magic-lanterns 
and  light-house  apparatus. 

The  regulator  of  M.  Jaspar 
(Fig.  34)  is  very  simple  in  con- 
struction. The  movable  rod  of 
the  upper  carbon-holder  is  the 
motor,  and,  by  its  weight, 
causes  in  its  descent  the  eleva- 
tion of  the  lower  carbon-hold- 
er to  which  it  is  united  by  a 
small  cord  passing  over  a  pul- 
ley. The  separation  is  effected 
FIG.  35.— F.  Cane's  regulator.  by  the  action  of  a  solenoid 

which  attracts  the  iron  rod  of 

the  lower  carbon-holder ;  as  this  action  is  much  more  power- 
ful at  the  beginning  of  the  course,  it  is  balanced  by  the  aid 
of  a  counter-weight  fixed  upon  the  transmission-wheel,  and 
turning  with  it,  so  that  the  lever-arm  of  this  counterpoise 


MULTIPLE  LIGHT,  OR  DIVISION,   REGULATORS.  Yl 

varies  inversely  with  the  action  of  the  solenoid.  A  second 
counterpoise,  whose  position  is  regulated  by  hand,  permits 
of  the  adjustment  of  the  apparatus  in  accordance  with  the 
intensity  of  the  current  to  be  regulated. 

The  iron  cores  attracted  by  the  solenoids  have  not,  as  in  the 
case  of  the  armatures  of  electro-magnets,  a  sharply-limited 
course.  To  limit  their  oscillations,  a  little  rod  of  iron  is  used, 
fastened  to  the  lower  carbon-holder,  and  plunging  into  a 
cylinder  filled  with  mercury ;  the  resistance  which  the  mer- 
cury offers  to  the  displacement  of  the  iron  rod  checks  and 
regulates  the  movement,  and,  in  consequence,  that  of  the  car- 
bons themselves.  On  account  of  this  disposition,  the  passage 
of  the  current  takes  place  under  excellent  conditions.  The 
regulator  of  M.  Jaspar  is  remarkable  for  the  regularity  and 
certainty  of  its  operation. 

In  this  same  category  may  be  placed  the  regulator  of  M. 
F.  Carre,  whose  movement  is  regulated  by  two  solenoids, 
curved  in  the  arc  of  a  circle.  The  armature  which  moves  in 
their  interior  is  of  S-shape,  and  oscillates  at  its  center  on  a 
fixed  point.  The  wire  is  wound  on  the  bobbins  so  that  both 
branches  of  the  armature  are  attracted  in  the  same  direction. 
Thus,  the  attractive  effect  is  doubled. 


CHAPTER  V. 

MULTIPLE  LIGHT,   OR  DIVISION,  REGULATORS. 

ALL  the  apparatus  which  we  have  studied  have  a  common 
defect,  derived  from  this  very  mode  of  regulation  by  the 
current,  whose  discovery  was  so  important  a  progress.  By 
using  the  whole  current  the  light  was  in  the  first  place  sub- 
ject to  all  the  reactions  due  to  the  work  done  by  the  current 
every  time  it  actuates  the  electro-magnet,  while  in  the  second 
place  an  almost  insurmountable  obstacle  is  created  in  the 
way  of  using  simultaneously  several  lamps  upon  the  same 
circuit.  To  appreciate  this  it  is  enough  to  study  that  which 
takes  place  when  two  apparatus  only  a,re  to  be  placed  in  the 
same  circuit ;  if  they  are  regulated  for  the  same  length  of 
arc,  it  is  necessary,  in  order  that  the  approaching  of  the  car- 


72  THE  VOLTAIC  ARC. 

bon  shall  take  place  in  each  lamp  in  similar  amount  and  in 
the  same  time,  that  their  respective  carbons  shall  be  consumed 
with  exactly  ,the  same  speed,  which  is  impossible.  Thus  in  a 
short  time  one  lamp  is  sure  to  present  a  wider  opening  than 
the  other.  Now,  as  the  electro-magnets  work  with  the  same 
current  and  symmetrically,  they  tend  to  work  almost  to- 
gether ;  in  the  apparatus  where  the  carbons  are  most  widely 
separated  they  will  return  to  the  normal  state,  in  the  second 
apparatus  they  will  at  once  come  in  contact.  If,  on  the  con- 
trary, they  are  arrested  together,  the  distance  between  the 
carbons  will  adjust  itself,  and  one  lamp  will  go  out ;  the  cir- 
cuit will  be  interrupted  and  the  second  will  also  go  out,  until, 
both  carbons  coming  in  contact,  both  will  light  up  for  a  new 
start.  This  would  be  still  worse  if  more  than  two  burners 
were  to  be  employed.  For  this  reason  these  apparatus  are 
designated  to-day  by  the  name  of  monopTiotes. 

There  will  be  no  difficulty  in  understanding  that,  when 
success  was  achieved  in  producing  electric  currents  in  all 
imaginable  conditions,  inventors  applied  themselves  with 
ardor  to  seek  the  solution  of  this  problem  so  inappropriately 
named  the  divisibility  of  the  electric  light.  It  has  been  solved 
by  the  employment  of  the  derived  current. 

I.   DERIVED- CURRENT,  OR  SHUNT-CIRCUIT,  LAMPS. 

When  a  current  finds  two  paths  open  to  it,  it  acts  like 
a  stream  of  water ;  it  divides  itself  between  the  two  paths 
directly  proportional  to  the  facility  of  passage,  or  inversely 
to  the  resistance.  Thus,  if  the  resistance  increases  on  one 
branch  of  the  circuit,  the  current  will  pass  in  larger  quantity 
by  the  other  wire.  In  the  polyphote  regulators  the  current 
is  thus  divided  into  two  portions,  one  of  which  goes  to  the 
voltaic  arc,  the  other  goes  to  the  electro-magnet  charged  with 
regulating  the  movement  of  the  apparatus.  The  wire  with 
which  this  electro-magnet  is  wound  is  much  finer  than  the 
rest  of  the  circuit ;  it  causes,  therefore,  high  resistance,  and 
ordinarily  only  suffices  for  the  passage  of  a  small  derived 
current,  insufficient  to  make  it  active.  But  when  the  resist- 
ance of  the  voltaic  arc  increases,  the  derived  current  in  the 
electro-magnet  increases  in  intensity,  and  this,  by  the  aid  of  a 
mechanism  analogous  to  those  which  we  have  already  de- 
scribed, releases  the  carbons,  which  approach  each  other, 


MULTIPLE  LIGHT,   OR  DIVISION,   REGULATORS. 


diminish  the  resistance  of  the  arc,  and  re-establish  the  pre- 
ceding state  of  affairs.  It  is  necessary,  as  will  appear  evident, 
to  properly  proportion  the  relative  resistances  of  the  arc 
circuit  and  electro-magnet  circuit.  With  this  distribution 
of  current  the  regulation  of  the  lamps  is  effected  in  an  inde- 
pendent manner,  because  the  same  quantity  of  electricity  will 
always  pass  from  one  lamp  to  another,  however  this  passage 
be  effected.  In  the  experiments  made  by  the  jury  of  the 
Universal  Exhibition  of  1878,  twelve  regulators  were  made  to 
work  upon  a  single  circuit 
of  an  alternating-current 
dynamo. 

The  first  employment 
of  a  derived  current  for 
regulating  the  advance  of 
the  carbons  was  made  in 
1855  by  MM.  Lacassagne 
and  Thiers ;  it  was  also 
combined  with  the  main 
current  of  the  lamp  so  as 
to  utilize  the  differential 
action,  as  we  shall  see  fur- 
ther on. 

In  1877  the  Lontin  com- 
pany again  employed  it  in 
the  Serrin  regulators  with 
which  they  experimented 
in  lighting  the  station  of 
the  Paris,  Lyons  and  Med- 
iterranean Railroad.  The 
apparatus  has  been  modi- 
fied thus :  the  electro-mag- 
net with  coarse  wire  of  the 

ordinary  model  is  replaced  by  an  electro-magnet  with  fine 
wire  A,  placed  vertically.  The  armature  B  placed  below  is 
attracted  when  the  derived  current  has  sufficient  intensity ; 
in  obeying  this  attraction  it  releases  the  rachet  and  permits 
the  carbons  to  approach  ;  it  permits  also  the  lower  carbon  to 
slightly  advance.  When  the  passage  of  the  lighting  current 
through  the  carbons  is  re-established,  the  armature  is  released, 
checks  the  movement,  and  moves  the  lower  carbon  enough  to 
produce  the  arc. 


FIG.  36. — Serrin  regulator  modified  for  derived 
current  by  the  Lontin  company. 


71  THE  VOLTAIC  ARC. 

Using  derived-current  regulators,  the  number  of  lamps 
that  can  work  upon  the  same  circuit  is  only  limited  by  the 
tension  of  the  current  at  disposal ;  thus  this  system  is  in  use 
to-day  in  a  great  number  of  regulators,  and  we  shall  show 
that  it  is  easily  adopted  in  former  systems  of  lamps.  We 
shall  only  describe  one  of  the  most  recent  of  such  apparatus ; 
we  refer  to  that  of  M.  Gramme. 

In  this  the  upper  carbon  is  the  only  one  that  moves,  and 
the  rod  which  sustains  it  turns,  by  means  of  a  rack,  a  series 
of  wheels,  the  axle  of  the  last  of  which  carries  a  rachet,  or 
scape-wheel,  with  long  teeth.  The  electro-magnet  with  fine 
wire  operates  an  armature  that  arrests  the  motion  of  this 
wheel,  which  is  arranged  in  a  peculiar  manner.  It  carries 
an  interrupter  which  cuts  off  the  derived  current  every  time 
the  armature  is  attracted  and  has  released  one  tooth  of  the 
scape- wheel.  The  action  of  the  spring  opposed  to  it  is  thus 
much  facilitated,  and  the  armature  forms  a  species  of  vibrator 
or  escapement  which  only  permits  the  scape- wheel  to  turn 
tooth  by  tooth.  An  electro-magnet  with  thick  wire  placed 
on  top  of  the  apparatus  lowers  by  its  armature  the  frame 
carrying  the  lower  carbon,  when  it  is  necessary  to  produce 
the  first  separation  for  lighting  the  lamp. 

Improvements  succeeded  each  other  rapidly ;  but,  when 
we  pass  from  the  laboratory  into  the  domain  of  actual  prac- 
tice, difficulties  show  themselves  at  every  step.  In  their  first 
attempts  a  new  trouble  was  encountered ;  the  polar  carbons 
are  consumed  quite  rapidly,  and  yet,  as  they  are  only  held 
by  one  extremity,  it  is  difficult  to  use  long  and  fragile  rods, 
and  to  direct  them  end  to  end  with  accuracy.  They  must  be 
frequently  renewed,  which  is  very  inconvenient  because  the 
lamps,  on  account  of  their  power,  are  generally  placed  very 
high  up.  It  is  a  cause  of  trouble  that  in  many  cases  is  in- 
admissible. 

To  avoid  this  objection  M.  de  Mersannes  invented  a  new 
mode  of  moving  the  carbons  which  permits  the  employment 
of  rods  of  all  sizes,  yet  only  introducing  into  the  circuit  the 
absolutely  necessary  length.  This  system  consists  in  passing 
the  carbons  between  grooved  wheels  which  turn  by  the  action 
of  a  spring,  and  in  turning  advance  the  carbons. 

The  apparatus  contains  two  electro-magnets  with  fine  wire 
placed  in  the  same  derived  circuit.  One  of  them  serves  to 
govern  the  movement  of  the  motor,  and,  in  consequence,  the 


MFLTIPLE  LIGHT,   OR  DIVISION",   REGULATORS. 


75 


C,  upper  cross-piece  acting  as  armature  for  the  elec- 
tro-magnet A  A. 

A  A,  electro-magnet  with  thick  wire  traversed  by 
the  light  current. 

E,  E,  counteracting  springs,  fastened  at  X,  Y  to  the 
bars  E,  E  of  the  movable  frame. 

D,  upper  carbon-rod ;  it  is  provided  with  a  rack,  and 
actuates  by  its  weight  a  train  of  wheels,  the  last  of 
which  is  an  escapement- wheel. 

B,  electro-magnet  with  fine  wire  traversed  by  a  de- 
rived current. 

F,  attachment  of  the  derived  circuit  to  the  rod  E. 
The  other  extremity  of  the  circuit  is  attached  to 
the  spring  N. 

I,  armature  of  the  derived-current  magnet  earned  by 
a  lever  L,  whose  other  end  carries  a  plate  S  de- 
signed to  catch  in  the  scape-wheel. 

L,  lever  pivoted  at  V. 

M,  contact-screw,  which  causes,  by  the  movements 
which  the  armature  I  gives  to  the  lever  L,  an  in- 
termittent contact  with  the  spring  N. 

K,  biiclge-piece  carrying  the  lever  L. 

U,  spring  opposing  the  action  of  the  armature  I. 

When  there  is  no  current  passing  through  the 
lamp  the  springs  E,  E  keep  the  movable  frame 
and  lower  carbon  raised  up ;  the  armature  I  is 
also  held  up  by  its  spring  U,  and  the  plate  S  stops 
the  movement  of  the  scape-wheel.  The  carbons 
are  now  separated.  This  break  of  continuity  forces 
the  current,  when  it  is  turned  into  the  apparatus, 
to  pass  into  the  derived  circuit  instead  of  going 
through  the  carbons.  The  electro-magnet  B  be- 
comes active,  attracts  its  armature,  the  lever  L 
swings  over,  and  the  plate  S  releases  the  scape- 
wheel.  The  rod  D  descends,  the  carbons  ap- 
proach, and  the  passage  of  the  cm-rent  is  estab- 
lished. At  this  moment  the  electro-magnet  A 
becomes  active,  and  attracts  its  armature  C ;  the 
lower  carbon  descends,  but  at  the  same  instant 
the  electro-magnet  B  becomes  inactive.  The  lever 
L  swings  back  the  other  way  and  the  scape-wheel 
is  caught.  The  checking  of  the  motion  of  the 
upper  carbon  and  the  lowering  of  the  lower  car- 
bon have  produced  the  necessary  separation  for 
the  establishment  of  the  arc.  The  screw  M  is 
then  in  contact  with  the  spring  N,  so  that,  as  soon 
as  the  main  current  weakens,  the  derived  current 
starts,  and  the  same  movements  are  reproduced ; 
but  this  derived  current  is  also  interrupted,  be- 
cause the  swinging  of  the  lever  separates  this 
screw  from  the  spring  and  breaks  the  circuit ;  it 
follows  that  the  counteracting  spring  acts  more 
readily,  and  the  releasing  is  less  prolonged.  The 
approach  of  the  carbons  takes  place  by  fractions 
of  millimetres,  and  the  arc  has  very  few  varia- 
tions. 


FIG.  37. — M.  Gramme's  derived- 
current  regulator. 


76 


THE  VOLTAIC  ARC. 


FIG.  38.— De  Mersanne  regulator. 

A,  barrel-spring  actuating  the  longitudinal  arbor  a  a. 

a  a,  arbor  which  transmits  the  movement  to  the  two  arbors  ft,  I  of  the  carbon-holders ;  it  is 
divided  into  two  unequal  parts  united  by  Cardan's  sleeves,  electrically  insulated. 

G  G',  rectangular  box  containing  the  arbor  a ;  the  part  G  is  also  mounted  at  s  on  hard  caout- 
chouc and  ivory,  so  that  all  the  pieces  of  one  of  the  carbon- 
holders  are  insulated  electrically. 

£,  J,  arbors  of  the  carbon-holders  driving  the  small  arbors  d,  d. 

d,  d,  transverse  arbors  which  transmit  the  movement  by  the 
wheels  e,  e,  e  to  the  feeding-guides  (Fig.  39). 

ff,  y,  feeding- wheels  which  advance  the  carbons  c  and  c  one 
toward  the  other  in  proportion  to  the  waste  due  to  the  com- 
bustion (Fig.  39). 

^,  A,  contact- guides  acting  to  insure  the  contact  between  the  car- 
bons and  the  feeding- wheels;  they  are  carried  by  a  small 
lever,  on  the  bearings  of  which  presses  a  spiral  spring  whose 
action  is  regulated  by  the  spring  i  i  (Fig.  39). 

0,  ratchet-wheel  placed  horizontally. 

B,  electro-magnet,  hollow,  and  with  fine  wire  helix;  the  two 
extremities  of  this  wire  are  connected  respectively  to  the  two 
carbon-holders,  that  is  to  say,  to  the  two  poles  of  the  main 
current,  so  that  it  is  only  traversed  by  a  desired  portion  of 
the  current.    When  the  separation  between  the  polar  carbons 
increases,  and  consequently  the  resistance  of  the  arc  to  the 
passage  of  the  principal  current,  the  derived  current  which 
circulates  in  the  magnetizing  helix  of  the  electro-magnet  im- 
mediately increases  and  develops  in  it  a  sufficiently  powerful 
magnetization  for  it  to  attract  its  armature  n. 


FIG.  39.— Section  of  the 
carbon-carrier  of  the 
De  Mersanne  regu- 
lator. 


MULTIPLE  LIGHT,  OR   DIVISION,  REGULATORS. 


77 


w,  armature  provided  with  a  detent  against  which  the  teeth  of  the  scape-wheel  or  ratchet 
strike ;  when  it  is  attracted,  these  teeth  escape,  the  carbons  begin  to  move,  and  approach 
each  other.  When  the  arc  has  attained  its  normal  length,  and  when,  in  consequence,  the 
passage  of  the  principal  current  is  re-established,  the  derived  current  almost  ceases  from 
passing,  and  the  electro-magnet,  becomes  almost  inert,  abandons  its  armature,  which  a 
spring,  0,  draws  forward ;  the  scape-wheel  is  caught  by  the  detent,  and  the  movement 
ceases,  to  start  anew  each  time  that  the  same  conditions  prevail. 

0,  spring  operating  the  armature  a. 

V,  limiting-screw  serving  to  regulate  the  position  of  the  armature  according  to  the  attractive 
force  developed  in  the  electro-magnet  by  the  derived  current. 

r,  screw  serving  to  regulate  the  detent  without  the  necessity  of  touching  the  screw  «?,  and 
without  deranging  the  regulation  of  tho  armature. 

C,  electro-magnet  whose  helices  are  in  the  same  derived  circuit  as  that  of  the  electro-magnet  B. 

q,  rod  fixed  upon  one  of  the  carbon-holders  and  carrying  on  its  upper  extremity  the  arma- 
ture of  the  electro-magnet  c. 

si  opposing- spring  of  the  armature  g.  The  action  of  this  spring  is  governed  in  such  a  way 
that  the  armature  can  not  be  attracted  except  when  the  current  attains  its  maximum  in- 
tensity, either  because  the  arc  is  not  yet  formed,  or  because  it  has  been  broken  by  too 
great  separation  of  the  carbons.  It  follows  that,  at  the  moment  when  the  current  is 
turned  into  the  apparatus,  the  armature  is  attracted,  and  the  carbon-holder  corresponding, 
drawn  by  the  rod  <?,  moves  like  a  scale-beam ;  it  remains  in  this  position  until  the  moment 
when  the  carbons  come  in  contact ;  then  the  passage  of  the  principal  current  is  re-estab- 
•  lished,  the  derived  current  disappears  altogether,  the  armature  is  set  free  and  is  drawn 
along  by  its  spring  with  the  carbon-holder ;  thus  there  is  produced  between  the  points  of 
the  carbons,  a  slight  separation  which  immediately  induces  the  formation  of  the  arc. 

progression  of  the  carbons.     The  role  of  the  other  is  to  pro- 
duce between  the  carbons  the  separation  necessary  to  cause 
the    voltaic    arc    to 
play  between  them ; 
for  this   purpose    it 
is    given    a  slightly 
greater  resistance, 
and  does  not  act  un- 
til the  carbons  come 
into  contact. 

Like  all  the  ap- 
paratus with  derived 
current,  M.  de  Mer- 
sanne's  regulator  is 
polyphote.  Fig.  38 
shows  the  horizontal 
type,  and  Fig.  39  the 
sectional  view  of  one 
of  the  carbon-hold- 
ers. 

With  this  regula- 
tor, the  duration  of 

the    period    Of   light-  FIG.  40.— The  Wallace  lamp. 


78  THE  VOLTAIC  ARC. 

ing  is  no  longer  limited,  because  the  carbons  made  by  M. 
Carre  are  a  metre  or  more  in  length  ;  they  can  last  through 
the  longest  nights  of  winter,  about  eighteen  hours,  without 
any  necessity  of  renewing  them — they  could  even  burn  longer. 
Mr.  Wallace  has  thought  of  another  mode  of  prolonging 
the  duration  of  the  period  of  lighting,  which  we  will  describe 
en  passant,  although  his  apparatus  does  not  come  in  the  cate- 
gory of  lamps  with  derived  current.  He  produces  the  voltaic 
arc  between  two  rectangular  plates  of  carbon  placed  verti- 
cally one  above  the  other  (Fig.  40).  The  lower  plate  is  fixed  ; 
the  upper  plate  is  movable  and  supported  by  the  armature  of 
an  electro-magnet  inclosed  in  the  box  A.  While  the  current 
does  not  pass  through  the  apparatus,  the  two  plates  touch ; 
as  soon  as  the  circuit  is  established  the  electro-magnet  raises 
the  upper  carbon  and  the  arc  is  established  ;  as  their  borders 
are  never  rigorously  parallel,  it  starts  at  the  point  of  least  re- 
sistance, and  then  travels  along  the  entire  length ;  when  the  dis- 
tance becomes  slightly  increased  by  the  combustion,  the  upper 
plate  descends,  the  arc  begins  again  to  travel  the  other  way, 
until  both  plates  are  quite  used  up — that  is  to  say,  in  about  a 
hundred  hours.  This  regulator  is  very  simple ;  but  the  incan- 
descence of  the  carbons  never  reaches  its  full  power,  and  the 
results  attained  in  the  production  of  light  are  not  very  good. 


II.     DlFFEKENTIAL   LAMPS. 

All  this  was  not  enough,  for  there  always  was  retained  the 
opposing  armature-spring,  a  spring  whose  inconvenience  we 
have  already  noted,  and  which  must  be  suppressed  to  avoid 
the  hand-regulating  required  each  time  the  intensity  of  the 
current  is  modified,  either  by  the  changes  in  the  number  of 
lamps  working  on  the  circuit,  or  by  the  variations  in  the  work- 
ing of  the  generators. 

Thus,  as  we  have  said  before,  it  is  MM.  Lacassagne  and 
Thiers  who  first  employed  an  electro-magnet  with  derived 
current  to  replace  the  opposing  spring  of  the  armature  of  an 
electro-magnet  with  thick  wire,  so  that  the  movement  of  this 
armature  was  due  to  the  differential  action  of  the  two  currents. 

In  their  apparatus  the  lower  carbon  was  alone  movable, 
the  rod  which  carried  it  being  fastened  to  a  piston  raised  pro- 
gressively by  mercury.  The  admission  of  this  mercury  into 
the  iron  cylinder  which  contained  the  piston  was  regulated 


MULTIPLE  LIGHT,   OR   DIVISION,   REGULATORS. 


79 


by  the  greater  or  less  compression  of  the  India-rubber  tube 
through  which  it  passed.  This  compression  was  exercised  by 
an  armature  subjected  at  the  same  time  to  the  actions  of  two 
electro-magnets,  one  with  thick  and  one  with  thin  wire.  Its 
sensibility  was  such  that  the  armature  remained  in  one  posi- 
tion, permitting  a  fine  stream  of  mercury  always  to  pass,  so 
that  the  approaching  of  the  carbons  takes  place  in  a  continu- 
ous and  uninterrupted  manner. 

On  the  same  principle  Dr.  Siemens  arranged  his  differ- 
ential lamp  (Fig.  41),  in  which  the  principal  current  and  the 


A,  stationary  lower  carbon  held  by  the  clarnp  b  on  the  lower 
cross-bar  of  the  frame. 

g,  movable  upper  carbon,  held  by  clamp  a  on  the  bar  Z. 

Z,  upper  carbon-holder,  serving  as  motor  to  the  system.  The 
upper  part  of  this  rod  is  made  into  a  rack. 

r,  ratchet-wheel,  driven  by  a  small  pinion,  which  itself  works 
into  the  rack  on  the  rod  Z. 

w,  p,  small  pendulum  provided  with  an  escapement  which  pre- 
vents the  wheel  turning  except  a  half-tooth  at  each  oscilla- 
tion. It  is  this  pendulum  which  governs  the  escapement. 

c  c,  A  A,  c2,  jointed  parallelogram  whose  upper  arm  c  c  is  fast- 
ened to  the  bar  of  soft  iron  S  S. 

T  T,  tine  wire  solenoid. 

R  R,  thick  wire  solenoid.  Both  act  together  on  the  bar  S  S, 
which  moves  freely  in  their  interior. 

x  y,  small  lever  pivoted  at  x  to  the  vertical  member  A  A  of  the 
parallelogram.  This  lever  has  at  y  an  indentation  which  re- 
ceives the  end  of  the  pendulum-rod  in  p. 

L,  L,  binding-screws  where  the  current  enters  and  leaves  the 
lamp. 

When  the  arc  is  started  and  is  of  proper  length,  it  is  the 
action  of  the  solenoid  R  R  under  the  influence  of  the  main 
current  that  predominates ;  the  bar  S  S  is  attracted  toward 
the  base,  and  changes  the  shape  of  the  parallelogram ;  the 
lever  y  x  descends  and  locks  upon  the  pendulum-rod  m  p, 
which  it  prevents  from  working. 

When  the  current  becomes  weak  by  the  lengthening  of 
the  arc,  the  derived  current  which  passes  through  the  sole- 
noid T  T  increases,  the  bar  8  S  is  attracted  upward  toward 
the  top,  and  the  parallelogram  tends  to  reassume  its  original 
shape.  The  lever  x  y  rises,  the  pendulum  m  p,  disengaged 
from  its  lock,  begins  to  oscillate  and  permits  the  ratchet  to 
turn.  The  bar  Z  descends,  and  brings  the  upper  carbon 
down  toward  the  fixed  carbon. 

The  parallelogram  is  connected  to  a  little  air-pump  or 
dash-pot  which  governs  its  movements.  In  case  of  extinc- 
tion or  breakage  of  the  carbons,  the  derived  current,  grown 
more  intense,  gives  the  solenoid  T  T  very  great  power ;  the 
bar  S  S  is  strongly  attracted,  and  operates  a  safety  contact 
of  platinum,  which  throws  the  lamp  out  of  circuit,  until  the 
rack  Z  has  descended  enough  for  the  arc  to  be  re-established 
between  the  carbons,  or  until  new  carbons  have  been  in- 
troduced. 

•       7 


FIG.  41. — Siemens  differ- 
ential lamp. 


80  THE   VOLTAIC   ARC. 

derived  current  act  simultaneously  in  two  opposite  directions, 
so  that  the  difference  between  their  relative  effects  regulates 
the  apparatus. 

As  in  the  Archereau  model,  only  one  of  the  carbons  moves. 
The  electro-magnetic  regulator  is  composed  of  two  solenoids, 
placed  one  in  prolongation  of  the  other  and  oppositely  wound, 
the  lower  one  having  a  short  and  thick  wire,  the  upper  one 
having  a  long  and  fine  wire  whose  resistance  is  nearly  a  hun- 
dred times  greater  than  that  of  the  principal  current.  They 
contain  a  soft  iron  tube  which  can  move  freely  up  and  down, 
and  whose  weight  is  balanced  by  that  of  the  other  movable 
pieces  of  the  apparatus.  Upon  this  tube  and  in  the  middle 
of  the  space  which  separates  the  solenoids  is  articulated  a 
lever  which  controls  the  movements  of  the  movable  carbon. 
As  is  evident,  the  tube  is  attracted  by  two  opposed  forces, 
and  the  equilibrium  depends  only  on  the  relation  of  the  re- 
sistances, a  relation  which  remains  the  same,  whatever  be  the 
variations  in  intensity  of  the  current.  A  small  piston,  which 
compresses  the  air  in  a  cylinder,  insures  the  steadiness  of  its 
movements.  By  this  system  ten  lamps  can  be  placed  on  the 
same  circuit,  and  independence  of  action  be  maintained. 

Differential  lamps  represent  the  last  phase  of  progress  in 
regulators,  and  we  have  only  to  note,  as  a  final  improvement, 
the  location  of  the  arc  below  the  machinery,  which  makes  it 
possible  to  suspend  the  lamp  and  better  utilize  its  light.  The 
use  of  a  single  movable  carbon  has  been  returned  to,  because 
it  has  been  recognized  that  the  fixed  position  of  the  luminous 
center  in  space  was  not  really  indispensable  except  for  opti- 
cal apparatus  or  mathematical  reflectors.  In  ordinary  light- 
ing, the  displacement  of  this  center,  due  to  the  consumption 
of  the  fixed  carbon,  is  much  the  less  appreciable  to  the  eye,  as 
the  lamps  are  generally  at  a  considerable  distance  ;  in  the 
case  of  lighting  by  reflection  on  stages  it  is  of  no  importance. 
In  simplifying  the  mechanism,  the  certainty  of  working  is 
increased,  and  the  price  of  the  apparatus  is  diminished,  and 
this  is  to-day  the  principal  question  to  be  solved  in  electric 
lighting. 

Inventors  have  availed  themselves  of  all  these  successive 
improvements,  and  excellent  pieces  of  apparatus  were  to  be 
found  at  the  Exhibition  of  Electricity,  giving  a  reasonably 
uniform  light,  as  long  as  the  current  supplying  them  ex- 
perienced no  extreme  changes.  We  shall  cite,  among  others, 


MULTIPLE  LIGHT,   OR  DIVISION,   REGULATORS. 


OP1  THE 

7EESIT7 

*  K« 

- 


FIG.  42.— Gerard  lamp. 

the  Crompton,  Pilsen  (Piette  and  Krizik),  Gerard,  Brush,  and 
Weston  lamps. 

The  Crompton  lamp  is  somewhat  of  the  Siemens  type, 
but  the  wheel-work  is  simplified  by  the  employment  of  an 
endless  screw  ;  this  screw  is  regulated  by  a  spring  brake, 
upon  which  act  in  opposite  directions  two  electro-magnets — 
one  with  thick,  and  the  other  with  thin  wire. 


82  THE   VOLTAIC   ARC. 

The  Pilsen  lamp  also  resembles  the  Siemens  type ;  it 
contains  two  superimposed  solenoids,  one  with  thick  wire, 
the  other  with  fine  wire.  The  upper  positive  carbon  is  the 
movable  one,  but  the  lower  carbon  receives  a  slight  lift- 
ing movement  destined  to  produce  the  separation  when  it 
drops  again.  The  plunging  armature  is  of  peculiar  shape  ; 
it  is  formed  of  two  elongated  cones  united  at  their  bases 
so  as  to  form  a  species  of  spindle.  M.  Krizik  has  found 
that  with  an  armature  of  this  shape  the  attraction  exer- 
cised by  a  solenoid  remains  equal  for  all  positions  of  the 
armature. 

In  the  Gerard  lamp  (Fig.  42)  the  upper  carbon  traverses  a 
tubular  electro-magnet  placed  above  the  apparatus,  and  de- 
scends freely  by  its  own  weight ;  but  its  descent  is  governed 
by  a  screw  acting  as  a  brake  and  placed  at  the  end  of  an  articu- 
lated lever  whose  other  end  carries  the  armature  on  which 
the  electro-magnet  acts.  An  opposing  spring  draws  back  this 
screw  and  sets  free  the  carbon,  when  the  derived  current  grows 
weaker. 

Between  the  uprights  of  the  frame  which  carries  the  lower 
carbon,  and  immediately  below  the  electro-magnet,  is  secured 
a  transverse  bar  of  insulated  iron  whicli  constitutes  a  second 
armature.  At  starting,  the  carbons  are  separated  ;  the  derived 
current  actuates  the  electro-magnet  which  draws  together  the 
two  armatures ;  one  sets  free  the  upper  carbon  which  de- 
scends, and  the  other  raises  the  lower  carbon ;  the  points 
touch ;  when  the  current  passes,  the  electro-magnet  grows 
weaker,  and  the  two  armatures  are  drawn  back  by  their 
respective  springs.  One  presses  the  brake-screw  upon  the 
upper  carbon  and  holds  it ;  the  other  descends,  drawing  with 
it  the  lower  carbon  ;  the  resulting  separation  creates  the  arc, 
and  the  movements  thus  continue. 

The  Brush  lamp  has  a  lower  fixed  carbon  ;  it  has  only  one 
solenoid,  on  which  two  wires,  a  thick  and  thin  one,  are  wound 
in  two  layers,  but  in  opposite  directions.  The  upper  carbon 
freely  descends,  but  the  rod  which  sustains  it  passes  through 
a  metal  ring  which  only  permits  the  descent  when  it  is  hori- 
zontal. When  it  is  raised  obliquely,  it  binds  upon  it,  and 
not  only  stops  the  descent,  but  raises  the  carbon  the  necessary 
distance  to  make  the  separation  and  produce  the  arc.  The 
solenoid  contains  a  soft  iron  tube,  provided  with  a  hook, 
which  effects  this  lifting  at  the  proper  time,  under  the  differ 


MULTIPLE   LIGHT,   OR   DIVISION,   REGULATORS. 


83 


ential  action  of  the  attraction  exercised  by  the  derived  current 
(Fig.  43). 

To  prevent  the  sudden  descent  of  the  carbon-holder,  and 
to  cause  it,  on  the  contrary,  while  it  is  free,  to  descend  with  a 
continuous  and  slow  motion,  the  upper  part  of  the  rod  is  hol- 
low, and  the  tube  thus  formed  is  filled  with  glycerine  (Fig. 


( 


FIG.  43.— Brush  lamp. 


FIG.  44. — Vertical  section  of  the 
upper  carbon-rod. 


44).  From  the  top  of  the  chimney  which  covers  it  a  rod  de- 
scends, carrying  a  small  copper  bell  forming  a  piston,  and 
only  leaving  a  slight  annular  passage  for  the  liquid  ;  the 
resistance  due  to  the  narrowness  of  the  passage  regulates  the 
movement. 


84 


THE  VOLTAIC  ARC. 


FIG.  45. — Kelation  of  the  two  carbon-rods  to  each 
other  in  the  double  lamp. 


FIG.  46.— Brush  double  lamp. 


The  same  means  is 
employed  to  make  the 
movements  of  the  plung- 
ing armature  of  the  sol- 
enoid easy,  and  the  little 
cylinder  filled  with  glycer- 
ine to  which  this  is  connect- 
ed may  be  seen  in  front 
of  the  bobbin  (Fig.  43). 

A  third  smaller  bob- 
bin, visible  in  front  of  the 
mechanism,  is  placed  in 
the  same  circuit  of  deriva- 
tion. It  offers  a  slightly 
increased  resistance,  and 
only  comes  into  action  to 
close  a  safety  contact  in 
case  a  too  prolonged  in- 
terruption of  the  voltaic 
arc  would  expose  the  de- 
rived-circuit wire  to  the 
danger  of  being  burned 
by  too  great  an  increase 
of  current. 

For  lights  of  long  du- 
ration the  Brush  lamp 
contains  two  pairs  of  car- 
bons very  ingeniously  ar- 
ranged. The  second  pair, 
governed  by  the  same 
mechanism,  do  not  act 
until  the  first  are  in  opera- 
tion, and  that  in  the  sim- 
plest possible  manner,  by 
means  of  the  distance 
maintained  between  them 
by  the  difference  of  height 
existing  between  the  two 
hooks  which  raise  the 
rings  (Fig.  45).  It  follows 
that  only  one  of  the  car- 
bons is  raised ;  the  arc 


86  THE   VOLTAIC   ARC. 

plays  between  the  carbons  thus  separated,  and  is  maintained 
there  until  they  are  used  up. 

The  complete  double  lamp  is  shown  in  Fig.  46. 

This  apparatus  has  worked  several  years  in  America.    It 


FIG.  48. — Brush  street-lamp. 

lights  notably  several  streets  of  New  York  (Fig.  47).  Fig.  48 
shows  the  establishment  of  a  double  lamp  upon  one  of  the 
pillars. 

The  Weston  lamp  (Figs.  49  and  50)  works  on  the  same  prin- 
ciples ;  the  movable  ring  is  replaced  by  a  lever  pierced  with  a 


MULTIPLE   LIGHT,   OR   DIVISION,   REGULATORS. 


87 


hole  for  the  carbon  to  pass  through.  This  lever  constitutes 
one  part  of  an  articulated  parallelogram,  one  of  whose  sides  is 
of  iron,  and  acts  as  armature.  This  is  actuated  by  an  electro- 
magnet, whose  branches  are  wound  alternately  with  thick  and 
thin  wire,  so  that  it  is  still  the  differential  action  of  the  two 
currents  which  governs  the  movements 
of  the  armature,  and  consequently  the 
movement  of  the  apparatus.  A  small 
plunger,  moving  in  a  cylinder  filled  with 
glycerine,  serves  as  moderator. 

[In  the  lamp  now  used  by  Mr.  Wes- 
ton  the  magnets  are  not  differentially 
wound,  but  the  main  and  shunt  mag- 
nets are  arranged  so  as  to  mutually  op- 
pose the  effect  of  each  other  in  moving 
the  upper  carbon-rod.  The  mechanism 
of  this  lamp  is  shown  in  Fig.  52,  and 
the  mode  of  action  more  clearly  in  the 
section  in  Fig.  53.  The  carbon-rod  R 
is  gripped  by  a  clutch,  shown  in  section 
in  Fig.  54,  operated  by  the  iron  cores 
of  the  main  circuit  magnet  A,  and  the 
shunt  or  fine-wire  magnet  B,  through 
the  medium  of  the  lever  L.  This  lever 
is  raised  by  the  core  of  the  main  mag- 
net, when  a  current  is  sent  through  the 
lamp,  causing  the  piece  I  to  bind  against 
the  rod  R,  which  is  then  carried  upward 
by  the  further  movement  of  the  core. 
As  the  arc  lengthens,  the  shunt-magnet 
B  becomes  strong  enough  to  check  the 
movement  of  the  lever  L,  the  two  mag- 
nets being  in  equilibrium  when  the  arc 
is  of  normal  length.  With  the  elonga- 
ting of  the  arc  due  to  consumption  of 
the  carbons,  the  power  of  the  magnet  B 
increases  and  draws  up  its  end  of  the 
lever  L  and  carries  down  the  carbon-rod, 
a  position  in  which  the  piece  I  ceases  to  bind  on  the  rod, 
this  is  allowed  to  slip  downward,  and  the  carbon  feeds.  A 
dash-pot,  D,  serves  to  prevent  too  sudden  movements  of  the 
lever  L. 


FIG.  49.— Weston  lamp. 


When  this  reaches 


88 


THE  VOLTAIC   ARC. 


A  lamp  of  the  same  class  is  that  of  the  Fuller  Company,  de- 
signed by  Mr.  J.  J.  Wood.     Its  construction  is  shown  in  Fig. 


E  R,  rod  of  the  upper  carbon-holder. 

C  C  C,  curved  lever  pierced  with  a  hole  through  which  the  rod  E  E  passes. 

A  A,  armature  which  is  fastened  to  the  lever  C  C.    The  springs  0,  N,  which  sustain  it,  only 
permit  vertical  movements. 

S,  opposing- spring  which  has  its  tension  regulated  by  a  screw  acting  on  an  elbow-lever. 

M  M,  electro-magnet  whose  branches  are  wound  alternately  by  a  thick  and  a  thin  wire  (Fig. 

51).  These  wires  are  wound  in  re- 
verse directions,  one  from  the  other, 
and  the  action  of  the  electro-magnet 
depends  on  the  differential  action  of 
the  two  currents  which  traverse  them, 
the  main  current  in  the  thick,  and  the 
derived  current  in  the  thin  wire. 
G,  movable  piston  working  in  a  small 
cylinder  filled  with  glycerine ;  the  rod 
of  this  piston  is  fastened  to  the  arma- 
ture A  A. 


IRON  CORE: 


FIG.  50.— Details  of  the  mechanism  of  the 
Weston  lamp. 


FIG.  51. — Section  of  one  of  the  differ- 
ential magnets  of  the  Weston  lamp. 


P,  plan  view  of  the  round  plates  which  form  the  piston  G  ;  there  arc  two,  one  fixed  on  the 
piston-rod  and  the  other  movable.  Each  has  three  triangular  notches,  and,  by  turning 
the  movable  plate,  the  size  of  the  openings  is  regulated.  The  resistance  which  the  piston 
offers  to  displacement  through  the  glycerine  prevents  the  too  sudden  movements  of  the 
armature. 

As  long  as  the  apparatus  is  in  normal  action,  the  action  of  the  main  current  is  in  the 
ascendant ;  the  lever  C  C  is  raised  up  by  the  armature,  the  rod  E  E  binds  in  the  hole,  and 
remains  immovable.  If  the  main  current  grows  weak,  the  derived  current  increases, 
and  produces  the  reverse  action ;  the  armature  left  free  is  drawn  back  by  its  spring  S  ;  the 
lever  C  C  lowers,  and  the  rod  E  E  is  allowed  to  descend.  Under  the  differential  action 
of  the  two  currents,  the  lever  C  C  takes  a  permanent  intermediary  position,  which  per- 
mits the  carbon-holder  to  slide  slowly  in  a  continuous  manner.  It  does  not  descend  en- 
tirely except  when  the  voltaic  arc  is  entirely  broken ;  in  this  case  the  rising  up  of  the  lever 
C  C  draws  the  rod  back  sufficiently  to  produce  the  separation  necessary  for  relighting. 

55,  and  the  relation  of  the  various  parts  in  the  diagram,  Fig. 

56.  The  connection  of  the  controlling  mechanism  with  the 
upper  carbon-holder  is  effected  by  gearing  instead  of    by 


MULTIPLE  LIGHT,  OR  DIVISION,   REGULATORS. 


89 


means  of  a  clutch,  as  in  the  lamps  of  Brush  and  Weston. 
This  carbon-holder  is  a  toothed  bar  or  rack,  into  which  gears 
a  pinion  connected  with  a  train  of  wheel- work.  It  moves  down- 
ward by  its  weight,  this  movement  being  governed  through 
the  intermediation  of  a  pawl  acting  on  one  of  the  wheels  of 
the  train  by  the  electro-magnetic  apparatus  shown.  In  Fig. 
56, //are  the  main  magnets  placed  in  the  arc  circuit  and  wound 
with  coarse  wire.  The  fine-wire 
magnets  7i,  h  are  placed  in  a  shunt- 
circuit,  and  oppose  by  their  action 
the  effect  of  the  main  magnets. 
The  current  enters  at  a,  passes 
down  by  the  holder  e  e,  through 
the  arc,  around  the  main  magnets, 
and  out  to  the  next  lamp  at  a'.  A 
rocking  lever,  j,  carrying  the  arm- 
ature i,  serves  to  control  the  de- 
scent of  the  upper  carbon.  The 
carbons  being  together,  the  magnets 
//  are  excited  on  the  passage  of 
the  current  and  attracts  the  arma- 
ture i.  This  movement  separates 
the  carbons  and  establishes  the 
arc.  The  winding  of  the  shunt 
and  main  circuit  magnets  is  such 
that  the  strength  of  these  magnets 
is  the  same  when  the  arc  is  of  nor- 
mal length.  When  the  arc  exceeds 
this  length,  the  attraction  of  the 
shunt  magnets  becomes  greater 
than  the  main  ones,  and  the  arma- 
ture i  is  attracted,  allowing  the 
lamp  to  feed. 

The  switch  b  enables  the  lamp 

to  be  turned  out  by  hand  when  desired,  by  throwing  its  end 
over  so  as  to  make  contact  with  o,  the  current  then  passing 
directly  from  a  to  a1  through  the  contact  o  and  lever  b.  This 
switch  is  operated  by  turning  the  key  b  (Fig.  55). 

The  ordinary  form  of  the  single-carbon  lamp  is  shown  in 
Fig.  57. 

The  single-carbon  lamp  is  converted  into  a  double-carbon 
one  for  all-night  operation  in  a  very  simple  manner.     It  is  also 


FIG.  52. — Mechanism  of  the  Weston 
lamp. 


90 


THE   VOLTAIC   ARC. 


constructed  for  use  in  reflectors.  In  this  case  both  carbons 
are  moved  toward  each  other  in  proportion  to  the  waste, 
the  upper  one  moving  at  twice  the  rate  of  the  lower.  As 


FIG.  53. — Vertical  section  of  operating  parts  of  the  Weston  lamp. 

both  carbons  are  positively  controlled,  this  lamp  can  be 
used  in  situations  where  it  will  be  subjected  to  constant 
jars,  such  as  in  the  head-light  of  a  locomotive.] 

Here  we  shall  stop  this 
enumeration ;  it  would  re- 
quire a  volume  to  describe 
all  the  apparatus  which  can 
give  a  good  light.  The  Elec- 
trical Exhibition  contained 
eighty  -  six  different  types, 
among  which  we  must  cite 
still  the  Berjot  and  Cance 
lamps.  Unfortunately,  the 
FIG.  54.— clutch  of  the  Weston  lamp.  regulation  and  maintenance 

need  special  workmen,  very 

skillful  and  very  careful ;  besides,  the  original  cost,  with  the 
indispensable  accessories,  is  always  quite  high ;  for  this  reason 
the  use  of  regulators  has  great  difficulty  in  becoming  general. 


III.    AUTOMATIC  SAFETY  APPARATUS. 

In  lamps  with  derived  circuit,  and  in  differential  lamps, 
the  employment  of  a  fine  wire  for  the  derived  circuit  requires 


MULTIPLE  LIGHT,   OR   DIVISION,   REGULATORS.  91 

the  addition  of  a  safety  contact,  which,  in  case  of  accident 
to  the  mechanism  or  to  the  carbons,  opens  a  passage  for  the 
current.  In  effect,  while  the  principal  current  is  interrupted 
by  a  prolonged  cessation  of  the  voltaic  arc,  the  current  finds 
only  one  way  to  pass,  namely,  the  derived  current  circuit, 
and  can  not  pass  in  sufficient  quantity  to  supply  the  other 
apparatus  upon  the  same  circuit ;  besides,  if  this  passage  of 


FIG.  55.— Mechanism  of  the  Wood  lamp. 

an  intense  current  in  a  wire  of  too  high  resistance  were  to  last 
too  long  a  time,  the  wire  would  heat  and  might  even  be  de- 
stroyed. 

To  prevent  variations  in  the  intensity  of  the  current  from 
causing  general  extinction,  the  extinguished  lamp  must  be 
replaced  by  a  resistance  equivalent  to  that  which  it  repre- 
sents, with  the  maximum  length  of  arc  admitted  by  its  regu- 
lator. 

To  satisfy  all  the  exigencies  of  electric  lighting,  a  certain 


92 


THE   VOLTAIC  ARC. 


number  of  supplementary  apparatus  have  been  invented,  of 
all  which  we  shall  only  examine  the  automatic  device  of 
Gerard,  and  Mersanne's  safety-box.  The  automatic  lighter 
of  Reynier  comes  also  in  this  category,  but,  as  it  is  designed 
for  another  system  of  lighting,  we  shall  study  it  at  the  same 
time  with  the  lamps  in  connection  with  which  it  was  designed 
to  operate. 

Gerard's  automatic  apparatus  has  for  its  object  the  cutting 
out,  in  case  of  accident,  of  the  lamp  to  which  it  is  appended, 


FIG.  56. — Diagram  of  the  working  parts  of  the  Wood  lamp. 

and  the  opening  of  a  direct  passage  to  the  current,  so  quickly 
that  the  other  lamps  on  the  same  circuit  shall  not  be  affected. 
It  consists  of  a  straight  electro-magnet  whose  bobbin,  wound 
with  fine  wire,  has  a  higher  resistance  than  the  lamp ;  of  a 
sliding  piece  with  two  rods  sliding  through  insulating  rings 
in  two  cups  containing  mercury ;  of  a  jointed  square  frame, 
carrying  on  one  side  the  armature  of  the  electro-magnet,  on 
the  other  the  hook  which  holds  the  suspended  sliding  piece. 


MULTIPLE  LIGHT,   OR  DIVISION,   REGULATORS. 


93 


If  the  lamp  becomes  extinguished,  the  current  passes 
through  the  electro-magnet ;  the  armature  is  attracted  and  the 
hook  releases  the  slider ;  the  rods 
fall  into  the  mercury-cups,  and 
the  current,  leaving  the  electro- 
magnet, passes  directly  through 
the  mercury  and  the  rods ;  by 
pressing  on  a  vertical  rod  placed 
below  the  slider,  the  former  cir- 
cuit is  re-established  and  the  lamp 
is  lighted ;  a  second  rod,  resting 
on  the  armature,  permits  the  un- 
locking to  be  done  by  hand,  so 
that  the  apparatus  can  be  used 
as  a  switch.  There  is  need,  of 
course,  of  one  for  each  lamp. 

The  safety-box  of  M.  de  Mer- 
sanne  goes  much  further  in  its 
surveillance ;  in  case  of  accident 
tending  to  interrupt  the  voltaic 
arc  for  a  long  enough  time  to  ex- 
pose the  derived  current  wire  to 
the  danger  of  being  burned,  such 
as  the  breakage  of  a  carbon,  for 
example,  it  so  substitutes  itself 
for  the  lamp  as  to  protect  the  de- 
rived circuit  parts  without  inter- 
rupting their  action.  It  follows 
that,  if  at  the  end  of  a  certain 
number  of  hours  the  lamp  is 
again  ready  to  operate,  it  assumes 
once  more  its  place  in  the  circuit, 
and  the  safety -box  ceases  to  act, 
and  is  then  in  condition  to  again 
work  whenever  it  may  be  neces- 
sary. 

This  apparatus  is  composed 
(Fig.  59)  of  an  electro -magnet, 
one  of  whose  arms  is  wound  with 
thick  and  the  other  with  thin 
wire.  This  last  forms  a  second  derived  circuit  which  does 
not  act  until  the  principal  current,  being  broken,  flows  in 


FIG.  57.— Wood  single  lamp. 


94  THE  VOLTAIC   ARC. 

excess  into  the  derived  current  wire  of  the  regulator.  In 
this  case  the  electro-magnet  of  the  safety-box  becomes 
active,  and  its  armature  brings  about  the  contact  between 


FIG.  58. — Gerard  automatic  cut-out. 


two  blocks  of  graphite ;  these  open  for  the  principal  cur- 
rent a  new  passage  through  a  resistance-coil  which  is  in- 
closed in  the  safety-box,  and  which  represents  exactly  the 


MULTIPLE  LIGHT,   OR  DIVISION,   REGULATORS. 


95 


resistance  of  the  arc  with  the  maximum  separation  of  the 
carbons  that  is  caused  by  the  regulator.  The  choice  among 
equivalent  resistances  is  not  an  indifferent  one  ;  that  which 

P  P',  electro-magnet  whose  arm 
P'  is  wound  with  thick  wire, 
and  placed  in  the  voltaic  arc 
circuit.  The  arm  P  is  wound 
with  fine  wire  and  placed  in 
the  derived  circuit. 

C,  armature  working  between 
contact-points. 

T,  support  of  the  armature. 

S,  bent  copper  wire  connecting 
the  armature  0  to  the  support 
T,  and  insuring  the  passage 
of  the  current. 

L,  corrugated  plate  of  copper,  of 
sufficient  section  for  the  pas- 
sage of  the  current ;  it  in- 
sures, by  its  flexibility,  a 
perfect  contact  at  E',  and  ab- 
sorbs the  vibrations  which 
might  be  produced  in  the 
armature  C  by  the  use  of 
alternating  currents. 

K  K',  blocks  of  graphite  be- 
tween which  the  safety-con- 
tact takes  place.  The  graph- 
ite is  used  here  because  it 
does  not  oxidize  at  high  tem- 
peratures, and  better  resists  the  breakage-sparks  which  appear  between  the  two  blocks 
each  time  they  are  separated.  It  is  quite  a  good  conductor  especially  when  heated. 

S  S',  supporting-rings  of  the  graphite  blocks. 

r,  spring  opposing  the  armature. 

a  d,  binding-screws  for  the  regulator-wires. 

m  m,  points  of  attachment  of  the  thick  wire  of  the  arm  P'. 

E,  auxiliary  resistance-coil. 

b  c,  points  of  attachment  of  the  wire  of  the  resistance-coil. 

E',  safety  contact. 

v,  screw  serving  to  limit  the  motions  of  the  armature  C. 

G  G',  metal  plates  replacing  the  wood  of  the  apparatus  in  places  where  it  might  be  burned 
by  the  graphite  blocks  heating. 

J,  wooden  support  of  the  electro-magnet. 

The  derived  circuit  of  the  safety-box  has  higher  resistance  than  that  which  actuates 
the  electro-magnets  of  the  regulator ;  it  only  permits  the  current  to  pass  if,  in  conse- 
quence of  prolonged  interruption  of  the  voltaic  arc,  the  current  flows  in  excess  through 
the  last ;  then  the  two  circuits  act  together ;  one  actuates  the  safety -box ;  the  other  con- 
tinues to  actuate  the  regulator.  The  passage  of  the  main  current  through  the  thick  wire  of 
the  arm  P  is  only  established  after  contact  at  E  between  the  graphite  blocks  takes  place ; 
it  has  for  end  to  reinforce  the  attraction  of  the  armature  C,  and  insure  a  better  contact. 


V 

FIG.  59.— Safety-box  of  M.  de  Mersanne. 


produces  the  least  heating  should  be  preferred.  M.  de  Mer- 
sanne has  observed  that  the  best  condition  was  to  give  the 
wire  of  the  resistance-coil  the  same  length  and  thickness  as 


96 


THE  VOLTAIC   ARC. 


that  of  the  induction- wire  in  which  the  current  is  originally 
produced. 

Graphite  is  used  here  just  as  mercury  was  in  the  pre- 
ceding apparatus,  because  metallic  contact-pieces  would  be 
burned  and  even  soldered  together  by  the  powerful  spark 
which  is  produced  each  time  the  auxiliary  circuit  is  broken 
by  the  play  of  the  apparatus  itself. 

The  arm  of  the  electro-magnet  that  is  wound  with  thick 
wire  is  placed  upon  the  auxiliary  circuit,  and  has  for  object 
the  re-enforcement  of  the  attraction  of  the  armature  and  the 

rendering  of  the  contact 
of  the  graphite  blocks  bet- 
ter and  more  certain. 

These  safety-boxes  can 
be  placed  anywhere,  no 
matter  how  far  from  the 
lamps,  in  the  locality  of 
the  machines  for  example ; 
they  then  serve  to  control 
the  general  lighting.  It 
follows  of  itself  that  the 
resistance-coil  can  be  sup- 
pressed, which  reduces  the 
safety-box  to  an  automatic 
regulator.* 

[The  Brush  automatic  cut-out  is  shown  in  the  diagram 
(Fig.  60).  The  normal  course  of  the  lighting  current  is  from 
the  terminal  a?,  through  the  coarse-wire  helix  of  the  regu- 
lating magnet  H,  H,  through  the  carbons  and  out  by  the  ter- 
minal y.  When,  however,  from  any  cause  the  path  through 
the  carbons  ceases  to  be  available,  the  current  is  diverted 
around  the  arc  through  the  path  formed  by  the  spiral  R,  the 
lever  B,  and  coil  T.  This  is  accomplished  by  means  of  the 
electro-magnet  T,  which  is  wound  with  a  thick  and  fine  wire 
coil,  both  in  the  same  direction.  The  fine  wire  is  in  the  same 
circuit  as  the  fine-wire  differential  helices  of  the  regulating 

*  [All  the  successful  modern  lamps  are  provided  with  a  safety  apparatus. 
This  is  termed  in  this  country  an  automatic  cut-out;  it  serves  simply  to  auto- 
matically provide  a  path  around  a  defective  lamp,  and  does  not  introduce  a 
resistance  equal  to  that  of  the  lamp  switched  out,  or  otherwise  regulate  the 
current  traversing  the  circuit.  This  is  done  by  apparatus  acting  upon  the  gen- 
erating dynamo.] 


FIG.  60. — Diagram  of  Brush  lamp  connections 
and  cut-out. 


MULTIPLE   LIGHT,   OR  DIVISION,   REGULATO^; :'[?.  fty 

magnet  H,  H.  When  the  arc  greatly  elongates,  the  magnet 
is  sufficiently  excited  to  attract  its  armature  A  on  the  end  of 
the  lever  B.  This  brings  together  the  two  contact-pieces  M 
and  M',  and  the  current  then  has  a  path  between  the  two  ter- 
minals x  and  y,  through  the  thick- wire  coil  of  the  magnet  T. 
This  path  will  remain  closed  as  long  as  that  through  the  arc 
is  interrupted,  as  the  attraction  of  the  magnet  T  keeps  the  con- 
tacts M,  M',  together. 

The  Weston  cut-out  is  shown  in  Fig.  61.  It  consists  of  an 
electro-magnet  in  the  main  or  arc  circuit,  arranged  so  as  to  al- 
low its  armature  to  drop  down  and  short-circuit  the  lamp, 
when  it  ceases  to  be  active,  owing  to  abnormal  lengthening  of 
the  arc.  A  coarse  coil  in  a  shunt-circuit,  wound  over  the 
main  coil  and  in  the  same  direction,  serves  to  cause  the  electro- 
magnet to  act  more  quickly  in  opening  the  short  circuit  when 
the  lamp  is  started.  The  apparatus,  which  is  in  a  very  com- 
pact form,  is  usually  placed  on  the  upper  frame  of  the  lamp. 

The  cut-out  of  the  Wood  lamp  is  shown  in  Fig.  56.  It  con- 
sists of  a  lever,  Z,  arranged  so  as  to  trip  the  curved  lever  m  and 
close  the  circiiit  at  n,  when  its  end  is  raised  by  the  pin  7c. 
This  pin  is  carried  by  the  armature  £,  and  stands  vertically  in 


MAIN 
LINE  -fc 


SHUNT 

KJ.  61.— Weston  automatic  cut-out. 


front  of  the  carbon-rod  e.  The  armature  i  is  attached  to  the 
rocking  lever,/  (Fig  55),  so  that  it  has  a  vertical  play.  As  ex- 
plained in  describing  the  lamp,  the  shunt-magnets  h  7i  grow 
stronger  as  the  arc  lengthens  and  attract  the  armature  i.  The 
rocking  lever  j  follows  their  movement,  and,  by  doing  so,  allows 
the  lamp  to  feed.  Stops  on  this  lever  prevent  it  going  upward 
more  than  a  determined  distance,  but,  on  account  of  the  vertical 


98  THE   VOLTAIC   ARC. 

play  of  the  armature  £,  this  can  continue  to  move  upward  un- 
der the  attraction  of  the  magnets  Ji  Ji.  When,  therefore,  the 
arc  becomes  of  abnormal  length,  the  armature  i  is  drawn  clear 
up,  and  the  lamp  short-circuited  through  n.~\ 


CHAPTER  VI. 

THE  JABLOCHKOFF  CANDLE. 

ONE  of  the  principal  reasons  which  for  a  long  time  re- 
tarded the  progress  of  the  electric  light  was  the  necessity  of 
employing  mechanical  regulators  for  bringing  together  pro- 
gressively the  carbon  rods  between  which  the  voltaic  arc 
played.  We  have  seen  in  the  preceding  chapter  that  these 
regulators  have  been  successively  improved  and  at  the  same 
time  simplified.  But  they  always  present  a  complication 
which  most  people  regard  with  distrust.  Things  were  in  this 
state  some  five  years  ago,  when,  in  1876,  a  Russian  officer,  M. 
Jablochkoff,  found  a  way  of  entirely  obviating  these  troubles, 
and  thus  put  the  electric  light  on  the  footing  of  daily  practi- 
cal use. 

The  great  merit  of  this  invention  is  its  perfect  simplicity, 
which  has  impressed  every  one,  and  silenced  those  who  wished 
to  see  in  the  electric  light  only  a  complicated  curiosity,  need- 
ing the  presence  of  a  professional  electrician.  Instead  of  plac- 
ing the  carbons  point  to  point,  M.  Jablochkoff  placed  them 
parallel,  side  by  side,  which  gave  the  simple  apparatus  the 
shape  of  a  candle,  and  suggested  its  name. 

The  two  rods  of  carbon  were  separated,  as  is  understood, 
by  a  band  of  insulating  material  that  the  arc  could  not  pierce, 
and  so  could  only  be  produced  between  the  two  points.  There 
was  no  longer  any  necessity  of  arranging  for  the  approach  of 
the  carbons  to  each  other  ;  they  remained  always  at  the  same 
distance  as  they  burned,  and  it  was  enough  to  choose  an  insu- 
lating material  that  would  burn  away  and  disappear  along 
with  the  carbons  so  as  not  to  form  an  obstacle  in  the  path  of 
the  voltaic  arc  ;  at  first  the  material  used  for  this  purpose  was 
that  out  of  which  china  is  made,  kaolin. 

The  apparatus  thus  constructed  could  be  placed  on  any 


THE  JABLOCHKOFF  CANDLE.  99 

kind  of  a  chandelier,  by  inserting  it  in  a  socket  just  as  would 
be  done  with  an  ordinary  candle  ;  the  only  requirement  is 
that  metallic  parts,  arranged  conveniently,  so  as  to  produce  a 
contact,  should  bring  the  electric  current  that  penetrates  by 
means  of  wires  in  the  standard  of  the  chandelier. 

The  lighting  of  the  candle  is  still  to  be  provided  for— that 
is  to  say,  the  starting  of  the  voltaic  arc,  which  is  done  in  regu- 
lators by  causing  the  two  points  to  approach  until  in  contact 
with  each  other.  Such  approach  is  here  impossible,  because 
of  the  interposition  of  the  solid  insulating  material.  To  effect 
the  lighting,  M.  Jablochkoff  reunites  the  two  points  of  the 
electrode  rods  by  a  very  small  slip  of  carbon  which  the  pas- 
sage of  the  current  brings  to  a  red  heat,  and  which  serves  as 
a  leader  for  the  voltaic  arc. 

Nevertheless,  the  apparatus  such  as  we  have  described  it 
is  subject  to  one  great  difficulty.  We  have  seen  already  that 
the  wasting  of  the  two  carbons  in  the  voltaic  arc  is  unequal. 
At  the  end  of  a  very  short  time  the  two  carbon-points  would 
no  longer  be  opposite  each  other,  and  this  distance  increasing, 
would  soon  render  impossible  the  passage  of  the  current. 

To  obviate  this,  M.  Jablochkoff  tried  giving  the  positive 
rod  of  carbon  a  double  thickness  ;  this  compensated  very  well 
for  its  greater  rapidity  of  consumption,  but  it  produced 
another  inconvenience.  The  thinner  negative  carbon,  offer- 
ing more  resistance  to  the  current,  grew  red  for  a  considerable 
part  of  its  length,  and  burned  up  rapidly. 

M.  Jablochkoff  then  had  an  idea  of  as  remarkable  sim- 
plicity as  the  principle  of  the  whole  system  :  it  was  to  change 
frequently  the  direction  of  the  current,  so  that  each  rod  of 
carbon  would  become  alternately  a  positive  and  a  negative 
pole ;  then  the  consumption  on  both  sides  should  be  equal. 
The  method  of  accomplishing  it  consisted  simply  in  the  use 
of  alternating  currents,  and  there  was  no  trouble  in  getting 
them,  because  the  magneto-electric  machine  then  in  most  ex- 
tensive use  and  the  most  powerful,  produced  currents  of  this 
description. 

The  apparatus  once  arranged,  all  its  parts  were  studied, 
so  as  to  be  perfected  as  much  as  possible.  At  first  it  was 
surrounded  by  a  coating  of  insulating  material,  covered  in 
its  turn  by  asbestus,  to  restrain  as  far  as  possible  the  capri- 
cious course  which  the  voltaic  arc  might  choose  to  follow 
(Fig.  62) ;  but  this  same  fitful  arc  showed  itself  wiser  than 


100 


THE   VOLTAIC  ARC. 


was  allowed  for,  and  this  thick  envelope,  found  useless  by 
experience,  was  dispensed  with  (Fig.  63). 

The  insulating  material  placed  between  the  two  carbons 
(called  in  a  general  manner  the  "  colombin  ")  was  also  changed. 


Type  of  1876. 


Type  of  1878.  Globe  containing  candles. 

FIGS.  62,  63,  and  64. — Jablochkoff  candle. 


The  kaolin  originally  employed  melted  at  the  end  under  the 
influence  of  the  voltaic  arc,  and  thus  created  between  the 
points  of  carbon  a  little  liquid  conductor  which  gave  a  pas- 
sage to  the  current.  A  voltaic  arc,  properly  so  called,  was  no 
longer  formed,  because  the  electricity  no  longer  traversed  the 


THE  JABLOCHKOFF   CANDLE.  101 

air ;  already,  so  to  say,  an  incandescent  light  was  produced. 
Unfortunately,  this  arrangement  of  kaolin,  favorable  in  itself, 
entailed  a  considerable  absorption  of  heat,  and,  in  conse- 
quence, a  considerable  increase  in  cost  of  maintaining  each 
lamp. 

To-day  the  kaolin  has  been  replaced  by  a  mixture  of  two 
parts  of  sulphate  of  lime  and  one  of  sulphate  of  baryta.  This 
mixture  is  not  melted  by  the  current ;  it  volatilizes  immedi- 
ately, and  thus  furnishes  incandescent  particles  which  in- 
crease the  brightness  of*  the  light  produced.  Besides,  it  is 
easier  to  manufacture  than  kaolin  ;  it  can  be  molded  or 
drawn  out  as  easily  as  plaster,  so  that  two  workmen  can  make 
nearly  fifteen  thousand  insulating  plates  per  day. 

A  Jablochkoff  candle,  then,  is  actually  composed  of  the 
following  parts  :  Of  two  carbons,  four  millimetres  thick  and 
twenty -five  to  thirty  centimetres  long,  always  cut  from  the 
same  stick,  so  that  they  will  always  have  the  same  composi- 
tion ;  of  a  colombin,  three  millimetres  wide  and  two  milli- 
metres thick,  whose  composition  we  have  already  given ;  of 
two  little  copper  tubes,  fifty-five  millimetres  long,  split  paral- 
lel to  their  axis  :  these  tubes,  into  which  the  carbons  pene- 
trate fifteen  millimetres,  have  for  object  the  insuring  a  perfect 
contact  between  the  carbons  and  the  jaws  of  the  candle- 
socket  ;  they  are  themselves  joined  by  means  of  an  insulator 
four  centimetres  long,  of  the  same  form  as  the  colombin,  but 
made  of  more  solid  paste  so  as  to  resist  the  pressure  of  the 
jaws.  The  whole  is  bound  together  at  the  junction  of  the 
colombin  and  the  lower  insulator  with  a  paste  of  silicate  of 
potash  base.  The  upper  ends  of  the  carbons  are  sharpened 
to  points  on  an  emery-wheel,  then  plunged  into  a  composition 
of  three  parts  of  coke  in  fine  powder  and  two  parts  of  plum- 
bago rubbed  up  with  gum -water  ;  this  species  of  cap  serves  to 
produce  the  lighting. 

The  most  important  point  to  be  insured  in  the  manufacture 
of  the  candle  is  the  perfect  adherence  between  the  carbons 
and  colombin  and  the  solidity  of  the  latter.  If  it  breaks  dur- 
ing the  burning,  or  if  a  piece  falls  from  it,  or  if  it  is  more 
quickly  consumed  than  the  carbons,  the  points  remaining 
project  above  it  and  the  arc  descends  into  the  cavity  thus 
formed ;  the  temperature  of  the  points  lowers,  and  the  light 
produces  those  reddish  tints  which  have  been  found  so  ob- 
jectionable. 


102 


THE   VOLTAIC  AKO. 


Each  candle  is  carried  in  a  metallic  pincers,  whose  two 
jaws  are  properly  insulated  ;  one  of  these  jaws,  A  (Fig.  65),  is 
hinged  and  is  pressed  by  a  spring  strong  enough  to  insure 

good  contact  ;  they  have 
semi-cylindrical  grooves  in 
which  the  brass  tubes  are 
received.  The  fixed  jaws 
are  united  to  the  same  sup- 
port and  connect  with  a  sin- 
gle return  wire,  R  R. 

At  the  end  of  two  hours 
the  exhausted  candle  must 
be  replaced,  and,  to  facili- 
tate the  operation,  the  lamp- 
posts have  several  candles 
arranged  to  succeed  each 
other.  The  globes  of  the 
Avenue  de  1'Opera  contain 
four.  When  the  first  can- 
dle goes  out,  a  commutator, 
hidden  in  the  foot  of  the 
lamp-post,  protected  from 
interference  on  the  part  of 
unauthorized  persons,  allows 
the  current  to  be  passed  into 
the  second,  then  into  the 
third  and  into  the  fourth. 
The  light  can  thus  be  kept 
going  for  nearly  eight  hours. 
Several  automatic  ar- 
rangements for  making  the 
current  itself  produce  the 
change  of  candles  have  been 
thought  of,  among  others  a 
mercury  commutator,  which 
we  will  describe  further  on ; 
the  duration  of  the  light 

4(  ^\       u  can  then  be  much  greater 

^^  *•  if  there  are  enough  candles 


Jfto.  65.— Sockets  of  Jablochkoff  candles  and 
switch  for  lighting  the  candles  successively 
by  hand. 


provided ;  and  a  period  of 
eighteen  successive  hours, 
without  the  candlebra  re- 


THE  JABLOCHKOFF  CANDLE.  103 

quiring  any  attention,  has  been  attained  in  a  Belgian  fac- 
tory. 

It  is  the  Jablochkoff  candle  that  has  brought  the  electric 
light  into  prominence  and  given  it  a  genuine  popularity.  An 
influential  company  was  formed  to  introduce  the  new  system  ; 
the  press  followed  the  exchanges  in  its  attention  to  it,  telling 
wonders  about  it,  so  that  every  one  wished  to  see  it,  and  pub- 
lic experiments  multiplied  on  all  sides. 

For  three  years  the  Avenue  de  1'Opera  has  been  lighted  by 
electric  candles,  the  large  stores  have  adopted  it  as  a  means 
of  advertising,  and  the  large  hotels  for  a  sign ;  it  is  a  feature 
of  all  the  public  fetes  in  the  great  cities  of  Europe  as  well 
as  in  Paris ;  and  to-day  there  are  not  less  than  twenty -five 
hundred  in  use  in  the  two  hemispheres,  especially  in  large 
workshops,  railroad- stations,  public  halls  and  squares,  ware- 
houses, theatres,  such  as  the  Hippodrome  in  Paris  (Fig.  66), 
and  in  several  palaces.  One  of  the  most  beautiful  examples 
of  this  mode  of  lighting  is  that  of  the  Moorish  saloon  of  the 
Continental  Hotel  in  Paris,  shown  in  the  frontispiece  of  this 
volume. 

Within  four  years  these  wonderful  little  candles  have 
found  means,  not  only  of  spreading  through  France,  Belgium, 
and  England,  and  Russia,  the  country  of  the  inventor,  but 
also  have  succeeded  in  penetrating  into  Greece,  Portugal, 
Brazil,  La  Plata,  Mexico,  and  even  into  those  places  where 
there  would  be  the  least  expectation  of  finding  improved  ma- 
chinery, such  as  the  palace  of  the  Shah  of  Persia,  of  the  King 
of  Cambodia,  and  the  residence  of  the  fierce  King  of  Burmah 
who  massacred  nearly  all  his  family. 

Its  extended  success  could  not  well  be  greater,  although 
it  is  far  from  combining  all  the  qualities  indispensable  to  a 
good  light.  The  light  of  the  electric  candle  is  fluctuating, 
and  its  variations  in  intensity  are  magnified  by  flashes  of  dif- 
ferent colors  which  often  mingle  with  its  light.  Those  who 
frequent  the  Avenue  de  1'Opera  may  have  remarked  that 
accidental  extinctions,  from  whatever  cause,  are  sufficiently 
numerous  to  render  the  exclusive  employment  of  the  lights  of 
this  system  in  the  public  service  very  dangerous.  In  exhibi- 
tions and  experiments,  where  great  care  has  been  bestowed 
upon  the  establishment  and  maintenance  of  the  apparatus, 
they  seem  to  work  a  little  better.  But  they  never  have  been 
able  to  compete  with  regulators  of  the  best  systems,  espe- 


LAMPS   WITHOUT  MECHANISM.  105 

cially  differential  lamps,  not  to  mention  the  systems  of  open- 
air  incandescence  which  supply  also  strong  centers  of  light 
much  more  agreeable  to  the  eye. 


CHAPTER  VII. 

LAMPS   WITHOUT  MECHANISM. 

THE  invention  of  the  Jablochkoff  candle  in  1876,  and  the 
immediate  impulse  given  by  this  discovery  to  the  use  of  the 
electric  light,  has  brought  out  during  the  last  five  years  a 
number  of  new  inventions.  These  inventions  are  for  the  most 
part  designed  to  obviate  the  necessity  of  using  the  tyrannical 
mechanical  regulators,  which  still  meet  with  public  distrust, 
in  spite  of  all  recent  improvements,  since  M.  Jablochkoff  has 
in  a  practical  way  shown  how  they  can  be  dispensed  with. 
While  all  inventors  agree  upon  the  result  to  be  reached,  they 
seek  to  attain  it  by  two  very  different  ways.  One  way  is  to 
change  the  nature  of  the  luminous  center  by  substituting  as 
the  source  of  light  for  the  voltaic  arc  the  incandescence  of  a 
body  which  this  arc  will  heat,  whether  carbon  electrodes,  as 
in  the  Reynier-Werdeman  lamps,  or  another  substance  intro- 
duced into  the  path  of  the  arc,  as  in  the  sun-lamp  ;  the  other 
way  is  to  preserve  the  regular  voltaic  arc,  but  to  regulate  the 
approach  of  the  carbons  without  the  use  of  mechanical  appa- 
ratus properly  so  called. 

I.   LAMPS  WITH  CONVERGING  CARBONS. 

The  first  lamp  invented  in  the  second  method  spoken  of 
above,  like  the  electric  candle,  is  due  to  a  Russian.  M.  Ra- 
pieff  invented  it  in  1878.  This  idea  is  of  still  greater  simplici- 
ty than  that  of  M.  Jablochkoff.  Imagine  two  rods  of  carbon 
placed  point  to  point  like  the  two  lines  of  a  V,  and  kept  in  this 
position  by  small  pulleys  or  rollers,  so  as  to  move  down  by 
their  individual  weight.  It  is  clear  that  as  these  rods  become 
consumed  they  will  to  the  last  remain  pressed  one  against  the 
other,  and  always  in  the  same  place  (Fig.  67).  Because  they 
touch,  the  voltaic  arc  can  not  play  between  them.  But  there 
is  nothing  to  prevent  us  from  arranging  below  them  two  other 


106 


THE  VOLTAIC   ARC. 


a,  a',  upper  carbons  forming  an  acute  angle  whose 
apex  is  the  positive  pole  of  the  lamp. 

*,  i',  lower  carbons  arranged  in  the  same  way, 
with  their  points  opposed  to  those  of  the  up- 
per carbons. 

d,  d',  carbon-holders. 

^,  cord  connecting  the  carbons  to  the  motor- weight 
W. 

f,  g,  e,  pulleys  carrying  the  cord  A,  so  placed  as 
to  preserve  the  oblique  direction  of  the  car- 
bons. The  lower  pulleys  establish  the  contact 
for  the  passage  of  the  current,  and  limit  the 
length  of  carbons  that  enters  into  the  circuit. 

S,  S',  rods  supporting  the  carbon-holders.  The 
rod  S'  and  the  positive  carbon-holder  are  in- 
sulated. The  rod  S  contains  a  rod  connected 
with  the  armature  of  an  electro-magnet  placed 
in  the  base  of  the  lamp,  and  designed  to  main- 
tain the  necessary  separation  between  the  two 
pairs  of  carbons  when  the  current  passes. 

W,  counterpoise,  which  constantly  acts  to  bring 
the  two  pairs  of  carbons  in  contact ;  on  ac- 
count of  their  obliquity  they  stop  reciprocally 
as  soon  as  they  touch.  The  cord,  in  passing 
around  the  pulley  of  the  counterpoise,  causes 
it  to  act  incessantly  on  both  pairs  of  carbons 
in  proportion  to  their  consumption,  so  that  the 
light-center  shall  not  change  its  place;  this 
arrangement  permits  the  use  of  direct  or  alter- 
nating currents. 

,The  lamp  relights  itself,  and  can  be  placed 
on  the  same  circuit  with  as  many  apparatus  as 
the  tension  of  the  current  will  admit  of. 


rods  forming  a  reversed  letter  Y. 
These,  of  course,  do  not  tend  to 
press  against  each  other  by  their 
own  weight,  but  the  same  move- 
ment is  produced  by  using  a  cord 
attached  to  them  and  passing  it 
over  pulleys  to  a  counterpoise 
heavier  than  the  rods.  The  vol- 
taic arc  will  then  play  between 
the  points  of  the  two  V's  placed 
at  a  proper  distance  from  each 
other — only,  each  pole  will  be 
FIG.  67.— Rapieff  arc  lamp.  formed  of  two  rods  instead  of 

one. 

To  light  the  lamp — in  other  words,  to  make  the  current 
pass  for  the  first  time— it  is  necessary  that  the  two  V's  touch 
each  other  for  an  instant.  This  manoeuvre  is  executed  by  the 


LAMPS   WITHOUT  MECHANISM.  107 

apparatus  itself  by  means  of  an  electro-magnet  arranged  so 
as  to  push  one  of  the  V's  in  advance  of  the  other  ;  this  electro- 
magnet is  worked  by  a  derived  current  from  the  main  current 
that  produces  the  voltaic  arc.  As  soon  as  the  arc  is  formed, 
this  current  returns  to  its  natural  course  ;  it  abandons  almost 
entirely  the  electro-magnet,  which  becomes  inactive  and  aban- 
dons the  movable  V ;  this  reassumes  its  regular  position,  which 
it  retains  as  long  as  the  lamp  continues  to  burn. 

M.  Rapieff's  system,  like  that  of  M.  Jablochkoff,  admits  of 
placing  five  or  six,  or  more,  lights  upon  the  same  circuit.  It 
has  given  good  results  in  England,  where  it  has  lighted, 
among  other  places,  the  press-room  of  the  printing-house  of 
the  largest  journal  in  the  world,  the  London  "Times."  The 
Rapieff  lamp  burns  seven  consecutive  hours  without  change 
of  carbons,  and  in  case  of  accidental  extinction  lights  itself. 
It  is  superior  in  these  two  points  to  the  Jablochkoff  candle, 
and  can  rival  it  in  luminous  intensity. 

M.  Rapieff  had  his  predecessors,  for  as  early  as  1846  an 
Englishman,  Edward  Staite,  invented  an  analogous  combina- 
tion ;  and  in  1875  a  Frenchman,  M.  Reynier,  constructed  also 
a  regulator  with  oblique  carbons,  which  he  soon  abandoned, 
to  seek  in  incandescence  another  solution  of  the  problem.  In 
his  turn  M.  Rapieff  was  imitated,  in  the  year  after  his  inven- 
tion— that  is  to  say,  in  1879 — by  a  Parisian  engineer,  M.  Ana- 
tole  Gerard. 

The  principle  of  his  apparatus  is  exactly  the  same  as  that 
of  M.  Rapieff ;  but  the  two  V's,  instead  of  being  placed  one 
under  the  other,  are  placed  beside  each  other  in  two  planes 
intersecting  each  other  like  the  two  opposite  faces  of  a  pyra- 
mid. The  rods  of  carbon  represent  in  some  sort  the  four  edges 
of  a  pyramid,  except  that  they  do  not  come  quite  together  at 
the  summit  (Figs.  68,  69).  It  must  be  understood  that  the 
pyramid  is  inverted,  the  rods  of  carbon  having  their  points 
directed  downward,  so  that  all  the  parts  capable  of  casting  a 
shadow  are  situated  above  the  luminous  center. 

In  addition  to  this  M.  Gerard  establishes  between  the  car- 
bons a  sort  of  magnetic  wind,  which  serves  to  repel  the  flame 
toward  the  end  of  the  rods,  and  thus  prevent  it  from  rising. 
This  magnetic  wind  is  formed  by  an  electro-magnet,  whose 
poles  exercise  a  repulsive  action  on  the  flames,  by  virtue  of 
the  well-known  laws  of  electro-magnetic  action,  as  they  are 
manifested  upon  a  magnetic  needle. 


108 


THE   VOLTAIC  ARC. 


In  the  Eapieff  and  Gerard  lamps,  as  in  the  candles,  alter- 
nating currents  are  usually  employed,  because  of  the  unequal 
consumption  of  the  positive  and  negative  carbons.  In  conse- 


Fio.  68. — G6rard  lamp.     General  appearance. 

quence  of  their  mode  of  production  these  currents  are  always 
accompanied  by  a  peculiar  noise,  more  intense  than  the  hiss- 
ing of  the  voltaic  arc,  to  which  it  is  added,  thus  constituting 


LAMPS  WITHOUT  MECHANISM. 


109 


FIG.  69. — Vertical  section  of  Gerard  lamp. 

A,  A',  tubular  carbon-holders,  forming  together  a  quadrangular  pyramid. 

B,  B',  carbon-rods. 

D,  plate  supporting  the  tubes  ;  the  tube  A  is  fastened  to  the  plate,  from  which  it  is  insulated 
by  an  ivory  plate ;  the  tube  B'  is  pivoted  by  means  of  a  hinge  to  the  support  D. 

F,  screw  serving  to  regulate  the  distance  of  the  carbons,  and  keep  the  length  of  the  arc  pro- 
portional to  the  tension  of  the  current. 

G,  spring  serving  to  maintain  the  separation. 

H,  screw  serving  to  regulate  the  tension  of  the  spring  G. 

I,  electro-magnet  with  fine  wire,  excited  by  a  derived  current  from  the  main  circuit. 

R,  armature  of  the  electro-magnet  I.     It  is  fastened  to  the  movable  tube  A'. 

M,  M',  bronze  rings  serving  at  the  same  time  to  guide  the  carbons  and  establish  the  passage 


110  THE  VOLTAIC   ARC. 

of  the  current ;  they  also  enable  one  to  limit  the  length  of  carbons  comprised  in  the  cir- 
cuit. 

C  C',  electro-magnet  with  thick  wire,  through  which  the  main  current  passes ;  its  poles  are 
prolonged  and  curved  inward  so  as  to  exercise  upon  the  current  which  forms  the  arc  a  suf- 
ficient influence  to  keep  it  between  the  points  of  the  carbons. 

On  starting,  the  points  of  the  carbons  are  separated  ;  the  main  current  not  having  any 
way  of  passing,  the  derived  current  starts  into  action.  The  armature  R  is  attracted, 
brings  the  carbons  in  contact,  and  opens  a  passage  for  the  main  current.  The  electro- 
magnet I  becomes  inactive,  the  spring  G  draws  the  carbons  back  the  proper  distance, 
regulated  beforehand  by  the  screw  E,  and  the  arc  begins  to  play.  This  burner  lights  it- 
self automatically,  and  admits  of  the  current  being  divided  among  several  lamps.  The 
length  of  the  carbon-rods  being  of  any  desired  length,  they  may  be  made  to  last  twelve 
hours  or  more  without  renewal. 

a  real  inconvenience  in  most  cases.  It  may  be  for  this  reason 
that  M.  Gerard,  abandoning  this  apparatus,  very  interest- 
ing from  its  certainty  of  action,  returned  to  regulators,  and 
has  invented,  since  then,  in  this  field,  so  crowded  already,  a 
new  combination,  of  which  we  have  spoken  in  the  preced- 
ing chapter. 

But  lamps  with  converging  carbons  can  work  very  well 
with  continuous  currents.  It  is  only  necessary  in  this  case  to 
give  the  positive  carbons  a  greater  length  than  that  of  the 
negative  carbons,  to  compensate  for  their  more  rapid  consump- 
tion. This  arrangement  ordinarily  is  free  from  any  objection. 

II.  RECENT  CANDLES. 

While  engaged  in  inventing  the  lamp  with  oblique  pencils, 
M.  Rapieff  was  also  busy  perfecting  the  Jablochkoff  candle, 
and  he  made  known  his  type  of  burner  in  the  same  year,  1878. 
This  type  greatly  resembles  that  of  M.  Wilde,  published  al- 
most at  the  same  time,  which  started  one  of  those  battles  for 
precedence  so  frequent  where  a  large  number  of  ardent  in- 
ventors are  exploiting  the  same  field.  M.  Wilde  is  generally 
thought  to  have  first  reached  the  goal,  and  it  is  his  candle 
which  we  shall  here  describe  at  greatest  length. 

Wilde's  Candle. 

Several  of  the  inconveniences  of  the  Jablochkoff  candle 
seem  due  to  the  "colombin,"  or  solid  insulating  material 
placed  between  the  two  carbons.  It  is  this  which  prevented 
the  approach  of  the  two  points,  necessary  for  automatic  light- 
ing. M.  Wilde  started  by  omitting  the  "colombin."  His 
candle  is  composed  of  two  parallel  rods  of  carbon,  four  milli- 
metres in  diameter,  analogous  to  those  of  Jablochkoff,  but 


LAMPS   WITHOUT  MECHANISM. 


Ill 


separated  only  a  space  of  three  miUimetres.  These  carbon 
rods  are  fastened  by  pincers  to  metallic  supports,  and  one  of 
these  supports  is  pivoted  so  as  to  permit  the  rod  to  incline  a 
little  to  come  in  contact  with  its  neighbor. 

This  is  its  natural  position,  that  which  it  occupies  of  itself 
en  the  apparatus  is  out  of  action.     When  the  current  is 


when 

sent  through,  it  passes  easi- 
ly from  one  point  to  the 
other,  and  lights  the  lamp. 
It  is  next  necessary  for 
the  rod  to  be  drawn  back 
to  produce  the  voltaic  arc. 
This  it  does  with  great 
quickness,  under  the  influ- 
ence of  an  electro-magnet, 
which  acts  upon  its  lower 
end,  and  thus  turns  it  upon 


UNIVERSITY 


A,  A,  A,  A,  supports  on  which  the  mov- 
able carbons  are  maintained  by  the 
springs  r ;  each  of  these  carries  at  right 
angles  a  plate  armature  for  the  electro- 
magnets a,  a,  a. 

R,  central  support  on  which  the  station- 
ary carbons  of  the  four  candles  are 
held  by  a  spring  S. 

a,  a,  a,  a,  electro-magnets  with  thick  wire 
traversed  by  the  current,  and  keeping 
the  carbons  separated  as  long  as  the 
current  passes. 

If  the  passage  of  the  current  is  in- 
terrupted, the  weight  of  the  supports 
A  makes  them  overbalance,  and  bring     / 
the  movable  carbon  in  contact  with    II 
the  stationary  one,  so  that  relighting 
takes  place.  FIG.  70. — Wilde's  candle.    Four-candle  holder. 

its  pivot.  This  electro-magnet  is  operated  by  the  current 
itself  ;  it  is  therefore  inactive  when  the  current  is  not  pass- 
ing, and  only  acts  when  the  current  reaches  it,  or  when  the 
lamp  is  lighted.  If  the  candle  becomes  extinguished  by  any 
accident  whatever,  the  current  no  longer  passes  through  the 
voltaic  arc  nor  through  the  electro-magnet ;  this  becomes  then 
inactive  ;  it  releases  the  movable  rod  which  leans  over  toward 
the  point  of  its  neighbor,  and  re-establishes  the  circuit.  Thus 
the  lamp  lights  itself  ;  all  is  done  so  quickly  that  the  extinc- 
tion is  hardly  perceptible. 


112  THE   VOLTAIC   ARC. 

Superior  to  the  Jablochkoff  candle  on  account  of  its  auto- 
matic lighting  and  relighting,  the  Wilde  lamp  also  excels  it 
in  the  duration  of  its  period  of  illumination.  The  Jablochkoff 
candles  last  only  one  hour  and  a  half,  and  it  is  with  great 
trouble  that  they  can  be  made  to  last  two  hours  by  lengthen- 
ing them.  In  the  Wilde  burner  there  is  no  limit  to  the  length 
of  the  carbon  except  the  fear  of  too  frequent  breakage,  because 
the  carbons  can  be  carried  down  into  the  foot  of  the  apparatus. 
They  have  been  made  sixty-five  centimetres  long,  which  rep- 
resents about  five  hours'  burning,  at  the  rate  of  twelve  centi- 
metres per  hour. 

If  the  foot  of  the  candle  remained  fixed,  as  in  the  Jabloch- 
koff system,  the  luminous  point  would  descend  thus  sixty -five 
centimetres  during  its  period  of  illumination.  Such  a  displace- 
ment would  be  entirely  inadmissible.  To  prevent  this  it 
sufficed  to  return  to  the  old  form  of  kitchen  candlesticks  or 
hotel  candelabra,  in  which  the  candle  rests  upon  a  small  socket 
sliding  in  the  tube,  and  which  can  be  lifted  up  little  by  little 
so  to  keep  the  end  of  the  candle  constantly  at  the  same  eleva- 
tion. In  a  like  manner  the  Wilde  candle  is  operated  after 
one  or  two  hours'  burning. 

Where  the  lighting  is  to  last  more  than  five  hours,  M.Wilde 
arranges  a  series  of  candles  in  a  circle  or  crown  on  a  round 
frame,  which  can  be  turned  by  hand  or  automatically  ;  the  ar- 
rangement resembles  quite  closely  that  of  the  Jablochkoff 
candles,  because  in  this  case  it  is  not  possible  to  make  the  car- 
bons so  long. 

M.  Wilde's  candle  can  be  turned  upside  down  and  work 
in  that  position,  which  avoids  the  casting  of  shadows  by  the 
different  parts  of  the  apparatus.  But  the  arc  then  is  in 
danger  of  abandoning  from  time  to  time  the  points,  and  of 
causing  by  these  oscillations  the  production  of  the  reddish 
flashes,  which  are  one  of  the  disagreeable  features  of  the  Jab- 
lochkoff candle. 

The  Jamin  Candle. 

The  Wilde  candle  belongs  to  1878.  The  following  year,  in 
1879,  another  appeared,  that  of  M.  Jamin,  which  was  modified 
frequently,  and  which  finally  borrowed  from  the  Wilde  candle 
its  most  characteristic  feature.  M.  Jamin,  professor  of  the 
Sorbonne,  and  also  of  the  Institute,  had  been  retained  by  the 
Jablochkoff  company  from  its  beginning  as  consulting  en- 


LAMPS   WITHOUT  MECHANISM. 


113 


A,  clay  plate  acting  as  support  for 
the  carbon-holders  and  direct- 
ing-frame. 

B,  directing- frame,  in  the  form  of  a 
flattened  groove,  in  which  the 
copper  wire  which  is  traversed 
by  the  current  before  it  reaches 
the  carbons,  is  wound. 

C,  upper  portion  of  the  frame,  con- 
structed of  soft  iron,  which  be- 
comes magnetized  under  the  in- 
fluence of  the    current.      This 
part  constitutes  the  electro-mag- 
net that  operates  the  carbons. 

D,  plate  of  iron,  pivoted  to  the  three 
movable  branches  of  the  carbon- 
holders,  to  which  they  impart 
the  same  movement.     As  soon 
as  the  current  passes  into  the 
apparatus  the    part    C,   or  the 
frame,  becomes  magnetized,  at- 
tracts this  plate,  and  keeps  the 
carbon  separated.     As   soon  as 
the  current  ceases  to  pass  the 
plate    falls    back,  and,    by    its 
weight,  forces  the  movable  car- 
bons to    approach    the    others. 
As  the  three  pairs  of  carbons  are 
of  unequal  lengths,  it  is  only  the 
longest  that  come  in  contact,  and 
only  one  candle  lights. 

a,  a,  a,  movable  carbons  in  the 
plane  of  the  directing-frame. 

J,  &,  #,  movable  carbons  in  planes 
perpendicular  to  that  of  the  di- 
recting-frame. 

H,  plates  pressed  each  by  a  spring 
and  resting  on  the  carbon -hold- 
ers #,  J,  b. 

The  action  of  these  plates  is 
restrained  by  a  brass  wire,  one 
of  whose  ends  is  kept  secured 
in  a  small  plate,  and  whose  other 

end,  bent  into  a  curve,  sustains  the  carbon-holder  6.  When  the  carbons  are  used  up,  the 
heat  of  the  voltaic  arc  melts  the  wire ;  the  spring  acts  and  draws  the  carbon-holders  to 
one  side,  so  that  the  passage  of  the  current  can  not  be  re-established  between  the  ends  of 
the  stationary  carbons. 

I,  binding-screws  for  entrance  and  exit  of  the  current. 

The  arrows  indicate  the  course  of  the  current,  which  traverses  the  directing  circuit, 
reaches  the  three  movable  carbons  at  the  same  moment,  passes  through  those  which  are 
in  contact,  and  lights  them.  It  may  be  seen  by  the  direction  which  it  follows  in  the  two 
branches  of  the  directing-frame,  and  hi  the  two  carbons  of  the  candle,  that  each  portion 
of  the  circuit  tends  to  make  the  arc  descend  and  remain  between  the  points ;  with  this 
burner  no  switch  is  required,  and  one  single  conductor  answers  for  all  the  candles  in  the 
same  circuit.  But  the  wire  that  is  wound  in  the  frame  introduces  an  important  resistance, 
which  makes  a  current  of  higher  tension  necessary ;  the  dimensions  which  the  frame 
ought  to  have,  for  efficacious  action,  does  not  allow  the  introduction  of  more  than  three 
candles. 


FIG.  71. — Jamin  candle. 


114  THE   VOLTAIC   ARC. 

gineer.  He  resigned  finally,  for  the  purpose  of  devoting  all 
his  time  to  the  improvement  of  candles.  His  principal  idea 
apparently  was  to  make  the  light  fixed,  by  preventing  it  from 
leaving  the  points,  so  that  he  could  turn  the  apparatus  upside 
down,  something  which  certainly  could  be  done  with  the 
Wilde  candle,  but  without  any  certainty  in  this  case  of  suffi- 
cient stability. 

To  reduce  this  idea  to  practice,  he  surrounded  the  candle 
with  a  certain  number  of  turns  of  the  wire  conveying  the  elec- 
tric current.  This  current  acts  upon  the  electric  light  as  it 
would  on  a  magnetized  needle,  and  it  is  easily  understood 
from  a  consideration  of  Ampere's  law  that  the  four  sides  of  the 
frame  exercise  an  accumulative  action  (Fig.  71).  At  first  M. 
Jamin  only  used  six  turns  of  wire,  then  he  ran  up  to  forty,  to 
obtain  a  more  energetic  action.  But  it  costs  a  great  deal  to 
obtain  this  action,  for  it  requires  a  current  of  higher  tension, 
and  thus  increases  to  a  certain  extent  the  cost  of  maintaining 
the  lamp.  The  frame,  too,  produces  a  disagreeable  effect. 
Finally,  it  gives  shadows  which  do  away  with  all  the  advan- 
tage obtained  by  reversing  the  candle. 

In  other  respects  M.  Jamin  preserved  the  arrangements 
of  M.  Wilde  for  doing  away  with  the  insulating  "colombin" 
and  the  automatic  reillumination.  Later  on  he  added  a  par- 
ticular mechanism  for  the  purpose  of  communicating  to  the 
carbons  an  oscillating  movement,  synchronous  with  the  pulses 
of  the  current.  According  to  him,  this  vibratory  movement 
should  enable  him  to  better  utilize  the  current.  This,  how- 
ever, has  not  proved  true  in  practice ;  experience  has  only 
made  the  quite  intense  noise  produced  by  these  vibrations 
more  remarked,  something  which  makes  the  use  of  these  burn- 
ers in  a  room  very  disagreeable. 

To  sum  up,  the  Jamin  candle  is  the  most  unstable  of  all, 
and  its  light  costs  more  than  that  of  others. 

Debrun  Candle. 

Finally,  we  must  speak  of  a  quite  recent  candle,  as  its  first 
invention  is  only  a  few  months  old  (December,  1880) ;  it  is  the 
candle  of  M.  Debrun.  This  is  a  provincial  production  ;  it  first 
saw  the  light  in  Bordeaux,  where  M.  Debrun,  Preparateur  d 
la  Faculte  des  Sciences,  was  commissioned  by  the  Jabloch- 
koff  Company  to  arrange  for  an  introduction  of  its  system  of 


LAMPS   WITHOUT  MECHANISM.  115 

lighting.  Having  been  struck,  like  all  others,  with  the  changes 
in  color  of  these  candles,  he  tried  to  overcome  the  difficulty, 
and  saw  at  once  that  he  would  have  to  do  away  with  the  insu- 
lating "colombin,"  as  M.  Wilde  had  already  done. 

The  Debrun  candle  lights  itself  automatically,  as  does  that 
of  M.  Wilde,  but  by  a  different  process.  In  place  of  inclin- 
ing one  of  the  carbon  rods  so  as  to  touch  the  other  rod  with 
its  point,  M.  Debrun  unites  them  by  a  transverse  priming, 
which  touches  them  at  their  bases,  and  starts  the  voltaic  arc. 
By  making  the  contact  at  the  base  it  is  possible  to  relight  the 
carbons,  even  when  they  are  very  short,  at  the  moment  of  their 
accidental  extinction ;  and  it  appears  that  the  voltaic  arc 
tends  to  fly  to  the  points  without  any  need  of  the  directing 
frame  with  which  M.  Jamin  surrounds  his  candle.  The  light- 
ing contact  is  actuated,  as  in  the  Wilde  candle,  by  an  electro- 
magnet ;  but  here  this  electro-magnet  is  placed  in  a  shunt 
circuit,  instead  of  in  the  main  circuit  of  the  voltaic  arc,  and  by 
the  details  of  construction  all  loss  of  energy  is  prevented. 

The  Debrun  candles  have  also  the  advantage  of  lasting 
much  longer  than  the  Jablochkoff  or  Jamin  candles.  They 
are  of  two  different  lengths.  One  lasts  three  hours  and  a  half 
and  costs  thirty-five  centimes  in  the  stores,  the  others  last 
six  hours  and  cost  sixty  centimes. 

This  is  cheaper  than  the  last  prices  of  the  Jablochkoff 
candles,  for  these  only  last  two  hours,  according  to  the  decla- 
ration of  those  most  interested.  Without  doubt,  the  cost  of 
establishing  the  electric  light  includes  many  other  elements 
than  this  one  ;  yet  it  is  worthy  of  notice  here. 

Although  still  in  its  infancy,  the  Debrun  candle  is  already 
introduced  in  the  Grand  Theatre  of  Bordeaux,  its  place  of 
birth,  in  several  cafes,  or  important  hotels,  and  several  stu- 
dios. It  has  lighted  several  public  fetes,  especially  the  Na- 
tional Fete  of  July  14,  1881,  at  Bordeaux,  and  the  district 
agricultural  fair  of  Alengon.  It  appears  that  it  will  soon 
light  the  Place  des  Quinconces,  also  in  Bordeaux. 

A  final  judgment  can  not  be  pronounced  upon  it  without 
having  followed  its  success  for  some  time  in  the  public  ex- 
periments ;  it  seems,  indeed,  very  liable  to  vacillate,  yet  less 
than  the  Jamin  candle. 


BOOK     III. 
THE    INCANDESCENT    LIGHT, 


CHAPTER  I. 

HISTORY  OF  INCANDESCENCE. 

THERE  are  two  very  different  modes  of  transforming  elec- 
tricity into  light,  one  could  almost  say  two  distinct  species  of 
electric  light :  the  light  of  the  voltaic  arc — which  is  that  of  all 
the  systems  with  regulators,  and  of  all  the  candles — and  the 
incandescent  light  of  a  solid  refractory  conductor,  which  can 
itself  be  produced  under  two  separate  conditions  quite  distinct, 
either  in  the  open  air,  or  in  a  closed  vessel  exhausted  of  air. 

In  the  first  case  the  incandescent  body  burns  more  or  less 
rapidly,  and  this  combustion  helps  to  produce  the  light.  In 
the  second  case  the  incandescent  body,  placed  out  of  the  in- 
fluence of  all  oxygen,  can  not  burn,  and  ought,  in  consequence, 
to  last,  if  not  forever,  at  least  very  long ;  this  is  termed  true 
incandescence,  because  in  this  kind  of  lighting  no  accessory 
phenomenon  helps  in  the  production  of  light. 

I.    THE  DEBUT  OF  PLATINUM. 

It  is  with  simple  incandescence,  out  of  contact  with  the  air, 
that  these  researches  commenced,  and  they  date  back  a  long 
time.  The  experiment  of  raising  to  incandescence  a  wire  of 
platinum,  by  passing  an  electric  current  through  it,  has  long 
been  well  known,  as  also  how  to  vary  at  will  all  the  conditions 
of  the  experiment,  for  it  was  enough  for  the  purpose  of  aug- 
menting the  intensity  of  the  light  to  diminish  the  diameter  of 
the  metallic  wire,  or  to  make  it  of  another  metal  which  was  a 
poorer  conductor  of  electricity. 

This  principle  was  applied  in  1841,  now  forty  years  ago, 


HISTORY   OF  INCANDESCENCE.  117 

by  an  Englishman  of  Cheltenham  named  Frederick  de  Mol- 
eyns,  who  used  a  platinum-wire  for  his  experiments.  Eight 
years  later  another  Englishman,  named  Petrie,  replaced  the 
platinum  by  iridium,  either  pure  or  alloyed  with  other  metals, 
and  patented  in  England  his  method  of  preparation  of  the 
iridium-wires  destined  for  electric  lighting. 

These  first  attempts  passed  almost  unnoticed,  and  it  is 
doubtful  if  they  even  were  remembered  nine  years  after,  in 
1858,  when  M.  de  Changy  published  his  process  of  lighting 
with  an  incandescent  platinum- wire  rolled  in  a  spiral,  analo- 
gous to  that  which  Mr.  Edison  used  again,  for  a  short  time, 
in  the  first  period  of  his  experiments.  Mr.  Jobard,  director 
of  the  Industrial  Museum  at  Brussels,  cited  no  precedent  in 
announcing  on  February  27,  1858,  to  the  Academy  of  Sciences 
at  Paris,  that  M.  de  Changy  had  succeeded  in  resolving  the 
problem  of  the  divisibility  of  the  electric  light.  This  was  the 
end  which  had  been  long  sought  for,  with  the  more  ardor  be- 
cause the  way  which  had  been  followed  seemed  to  lead  to  no 
solution. 

The  invention  of  M.  de  Changy  made  a  great  noise  at  once ; 
but  the  noise  soon  ceased  in  presence  of  the  undeniable  in- 
conveniences, which  made  the  system  almost  impossible  in 
practice.  The  principal  one  of  these  inconveniences  is  the 
ease  with  which  platinum  melts  if  the  temperature  at  which 
it  furnishes  a  good  white  light  be  exceeded.  A  slight  varia- 
tion in  the  intensity  of  the  electric  current  is  sufficient  to  pro- 
duce this  injurious  heating,  and  as  yet  they  were  unable  to 
regulate,  even  in  an  approximate  manner,  the  force  of  the  cur- 
rent employed. 

The  platinum-wire  lamp  was  condemned  to  remain  at  rela- 
tively low  temperatures,  so  as  not  to  risk  its  melting  all  at 
once  and  disappearing.  Now  at  these  low  temperatures  plat- 
inum gives  naturally  a  decidedly  colored  light,  yellow,  or 
sometimes  red,  and,  worse  yet,  not  bright  enough  for  the 
needs  of  practice  even  the  least  exacting.  A  red-hot  wire  can 
not  be  called  a  lamp,  and  all  the  cooks  would  prefer,  without 
hesitation,  the  poorest  of  candles  of  six  to  the  pound. 

II.    THE  DEBUT  OF  CARBON. 

A  substance  less  fusible  than  the  metals  then  had  to  be 
sought  for,  so  that  the  temperature  could  be  raised  without 


118  THE  INCANDESCENT  LIGHT. 

fear.  Such  were  not  wanting ;  but  the  most  of  them  could 
not  be  reduced  to  fine  wires,  and  almost  all  of  them  burned 
readily,  which  was  worse  yet  than  melting.  In  producing  in- 
candescence in  a  vacuum  the  danger  of  combustion  can  be 
avoided.  On  this  basis,  difficult  as  it  was  to  realize  at  this 
time,  carbon  engaged  the  attention  of  inventors  almost  at  the 
same  time  as  platinum,  for  the  first  patent  in  this  direction 
was  taken  out  in  1845  by  an  American  named  King,  four  years 
after  the  first  experiments  with  incandescent  platinum  tried 
by  the  Englishman  Frederick  de  Moleyns. 

The  origin  of  the  incandescent-carbon  lamp  is  surrounded 
by  a  sad  mystery.  We  are  at  liberty  to  believe  that  the  true 
inventor  was  a  scientist  of  Cincinnati,  named  J.  W.  Starr, 
and  whose  work  to-day  is  forgotten  even  in  America. 

Like  all  true  philosophers,  J.  W.  Starr  was  poor.  But  he 
made  the  acquaintance  of  the  great  philanthropist  Peabody, 
the  founder  of  several  great  scientific  institutions  of  the 
United  States,  and  whose  name  is  as  celebrated  on  this  side 
of  the  Atlantic  as  in  the  New  World.  Peabody  showed  him- 
self generous,  as  usual,  and  gave  the  inventor  all  the  money 
he  required  to  submit  his  processes  to  the  great  savans  of 
England.  At  this  time  the  young  American  showed  himself 
a  submissive  and  devoted  disciple  of  science,  and  did  not  fol- 
low the  custom  of  this  day,  in  believing  that  he  had  the  right 
to  consecrate  to  himself  alone  his  great  discoveries. 

J.  W.  Starr  sailed  then  for  the  Old  World,  bringing  with 
him  as  agent  a  man  more  accustomed  to  business  affairs,  and 
provided  with  a  smaller  quantity  of  philosophic  naivete,  who 
would  not  let  the  natives  of  perfidious  Albion  get  the  better 
of  him  ;  this  business  man  was  King. 

When  he  arrived  in  England  J.  W.  Starr  set  to  work  to 
prepare  a  great  public  demonstration.  He  set  up  a  great  can- 
delabra of  twenty- six  lights,  to  symbolize  the  twenty-six 
united  States  of  North  America,  which  have  since  then  in- 
creased greatly  in  number.  The  great  physicist,  Faraday, 
assisted  at  these  experiments,  admired  them  greatly,  and  prom- 
ised him  success. 

These  experiments  terminated,  Starr  and  King  re-embarked 
for  the  United  States,  without  doubt  to  report  to  Peabody  the 
sanction  of  European  science,  and  ask  of  him  pecuniary  means 
to  realize  the  invention  on  a  large  scale,  and  enable  it  to  enter 
the  industrial  domain.  But  the  day  after  they  embarked, 


HISTORY   OF   INCANDESCENCE.  119 

Starr  was  found  dead  in  his  berth,  and  it  was  never  known 
exactly  how  he  came  to  his  death. 

King  had  taken  out  a  patent  in  his  own  name.  He  then 
declared  that  gas-carbon  gave  better  results  than  others,  and 
referred  to  the  necessity  of  placing  it  in  a  vessel  exhausted  of 
air  to  avoid  its  combustion.  King  also  remarked  that  several 
apparatus  of  this  kind  could  be  placed  upon  the  same  circuit, 
as  Starr  without  doubt  had  done  in  his  experiments  before 
Faraday,  and  that  this  circuit  could  receive  its  electricity 
either  from  a  battery  or  from  a  magneto-electric  machine, 
types  of  which  were  then  known,  it  is  true,  but  the  machines 
were  very  weak. 

A  year  after  the  American  King,  in  1846,  two  Englishmen, 
Greener  and  Staite,  who  may  have  had  little  knowledge  of  the 
experiments  of  J.  W.  King  in  London,  also  took  out  a  patent 
for  a  lamp  with  incandescent  carbon  analogous  to  that  of 
King.  They  added  to  it,  however,  a  new  process  :  the  em- 
ployment of  aqua  regia  (nitro-muriatic  acid)  to  free  the  carbon 
of  its  impurities,  and  to  give  thus  more  regularity  to  the  light 
and  at  the  same  time  a  greater  solidity  to  the  ii lament. 

In  spite  of  a  beginning  that  seemed  to  promise  a  great  deal, 
the  whole  aifair  fell  into  oblivion  for  thirty  years.  It  is  prob- 
able that  Peabody  did  not  wish  to  continue  conferring  upon 
King  the  favors  he  reserved  for  Starr,  and  that  King  did  not 
find  others  to  supply  funds  to  carry  on  an  enterprise  very  haz- 
ardous at  this  epoch,  even  in  the  eyes  of  Americans.  With 
King  reduced  to  impotence,  the  idea  now  disappeared  from 
view  under  other  preoccupations,  for  the  public  soon  cease  to 
think  over  an  enterprise  which  does  not  succeed  at  the  first 
attempt,  when  general  opinion  does  not  run  in  the  same  direc- 
tion. 

III.  THE  RUSSIAN  LAMPS. 

It  was  in  Russia,  about  1873,  that  the  light  by  incandescent 
carbon  came  at  last  out  of  the  oblivion  in  which  it  had  slept 
for  twenty-seven  years.  A  Russian  physician,  M.  Lodyguine, 
invented  a  lamp  founded  on  this  principle,  ancj  which  won 
him  one  of  the  grand  prizes  of  the  Academy  of  Sciences  of  St. 
Petersburg. 

In  describing  M.  Lodyguine's  labors,  M.  Wilde,  member  of 
the  academy,  charged  with  the  report,  very  well  expressed  all 
the  advantages  which  result  from  the  employment  of  carbon 


HISTORY   OF   INCANDESCENCE.  121 

instead  of  platinum  for  the  production  of  the  incandescent 
light. 

Carbon,  at  the  same  temperature,  possesses  a  much  higher 
radiating  power  than  platinum ;  the  calorific  capacity  of  carbon 
is  much  less,  so  that  the  same  quantity  of  heat  brings  the 
carbon  pencil  to  a  higher  temperature  than  it  would  do  in 
the  case  of  a  platinum  wire.*  Besides,  the  electric  resistance 
of  the  carbon  is  about  250  times  greater  than  that  of  platinum, 
so  that  the  carbon  pencil  can  be  much  thicker,  and  yet  reach 
the  same  temperature  as  the  metal.  Finally,  carbon  is  infusi- 
ble, and  its  temperature  can  be  raised  freely  without  danger 
of  melting. 

M.  Lodyguine's  lamp  was  formed  of  small  needles  ending 
in  prisms,  and  made  of  retort-carbon,  fastened  between  two 
insulated  pincers,  which  placed  them  in  contact  with  the  two 
branches  of  the  circuit,  almost  the  same  as  is  done  with  the 
Jablochkoff  candle.  For  preventing  them  from  burning,  they 
first  used  to  close  them  up  in  vessels  exhausted  of  air ;  but, 
as  the  removal  of  air  by  means  of  an  air-pump  was  a  quite 
costly  operation  for  practical  manufacture  in  the  conditions 
under  which  they  then  worked,  they  generally  left  the  appa- 
ratus full  of  air,  carefully  sealing  it  hermetically,  so  as  to 
prevent  oxygen  from  renewing  itself  after  having  disappeared 
by  combining  with  the  carbon. 

But  there  may  be  produced  a  sort  of  combustion  with  the 
imprisoned  oxygen,  and  it  was  without  doubt  one  of  the 
causes  that  made  the  carbon-rods  break  very  frequently. 
These  ruptures  caused  long  interruptions,  for  it  was  not  easy 
to  replace  the  broken  carbons.  It  seems  that  quite  a  satis- 
factory light  could  be  produced  from  four  lamps  of  this  kind 
placed  on  one  electric  circuit  supplied  by  one  of  the  strong 
machines  with  alternate  currents  of  the  Compagnie  V Alli- 
ance. 

M.  Kosloff,  of  St.  Petersburg,  to  whom  was  intrusted  the 
importation  and  introduction  into  France  of  the  Lodyguine 
lamp,  improved  it  in  certain  points  ;  for  instance,  by  employ- 
ing a  new  metal  for  the  metallic  supports  holding  the  carbon 
pencils,  which  supports  melted  very  often  in  the  earlier  type. 
M.  Konn,  in  1875,  and  M.  Bouliguine,  in  1876,  invented  other 
lamps  founded  on  the  same  principles,  with  different  arrange- 

*  [Calorific  capacity  ceases  to  be  an  element  to  be  taken  into  account  when 
the  permanent  temperature  is  attained.] 


122 


THE  INCANDESCENT  LIGHT. 


ment  of  parts  and  of  better  working  capacity.  Figure  73  will 
suffice  to  give  an  idea  of  these  apparatus. 

Biit  all  these  Russian  lamps,  of  which  several,  it  is  true, 
were  invented  in  Paris,  had  a  common  defect,  and  a  capital 
one  at  that :  the  carbon-rods  placed  between  two  larger  pieces 

A,  copper  socket  on  which  are  fixed  two  binding-screws 
N,  one  of  which  is  insulated,  for  attachment  of  the 
conductors. 

K,  small  cylindrical  box  containing  a  safety  -  valve, 
which  only  opens  from  within  to  without.  It  is 
provided  with  a  nipple  for  receiving  the  tube  lead- 
ing to  the  air-pump,  when  a  vacuum  is  created  in 
the  bell  B. 

B,  globe  enlarged  at  its  upper  part,  and  held  upon  its 
base  by  a  brass  screw-collar,  abutting  against  an 
India-rubber  ring. 

D,  vertical  rod,  electrically  insulated,  and  provided  at 
its  upper  end  with  a  small  horizontal  plate  G.    This 
plate  contains  five  small  cavities  to  receive  the  cop- 
per ends  of  the  carbon-holders. 

C,  bar  composed  of  a  tube  fastened  to  the  base,  and  of 
a  copper  rod,  split  for  a  part  of  its  length  so  that  it 
can,  with  a  slight  effort,  be  forced  down  into  the 
tube.     This  rod  is  supplied  with  a  horizontal  plate 
at  its  top,  pierced  with  five  holes. 

E,  carbons  placed  between  the  two  plates.     They  are 
fastened  into  small  blocks  of  carbon  O  0  ;  the  bot- 
tom blocks  have  small  rods  of  copper  of  equal 
length,  by  which  they  rest  upon  the  lower  plate ; 
the  upper  blocks  are  also  provided  with  rods  which 
pass  through  the  holes  in  the  upper  plate  ;  as  they 
are  of  unequal  length,  the  lever  I  only  rests  upon  a 
single  one  of  them. 

I,  lever  pivoted  on  the  top  of  the  rod  C.     It  rests  suc- 
cessively upon  the  rods  of  different  blocks,  and  de- 
termines the  direction  of  the  current. 
H,  copper  rod  on  which  the  lever  rests  when  all  the 

carbons  are  burned,  and  which  permits  the  current  to  pass  to  the  other  lamps. 
M,  copper  tube  receiving  the  debris  of  burned  carbons. 

The  five  carbons  are  placed  between  the  plates,  and  the  lever  I  is  lowered,  which 
rests  upon  the  longest  one ;  the  globe  is  pumped  out  and  the  vacuum  formed.  The  cur- 
rent is  then  passed  into  the  lamp ;  the  little  carbon  E  reddens,  whitens,  and  becomes 
luminous  ;  it  is  consumed  little  by  little,  the  rod  breaks,  and  the  light  disappears.  At 
once  the  lever  I  drops  down  upon  another  rod  and  the  light  is  re-established  almost  im- 
mediately with  the  next  carbon.  This  continues  until  the  five  carbons  are  used  up. 

were  disintegrated  sooner  or  later  by  an  action  which  was  not 
combustion,  for  it  took  place  without  oxygen.  The  pencil 
grew  thin  in  the  center  arid  gradually  ended  by  breaking  ;  it 
then  had  to  be  replaced,  and  this  substitution  had  become  the 
principal  problem  placed  before  the  inventors  of  incandescent 
lamps. 


FIG.  73.  —  Incandescent  lamp 
Konn,  in  a  closed  vessel. 


INCANDESCENCE  IN   THE   OPEN  AIR.  123 

CHAPTER  II. 

INCANDESCENCE  IN  THE  OPEN  AIR. 

WE  have  now  seen  in  the  preceding  chapter  the  difficulties 
under  which  the  incandescent  lamps  up  to  1874  labored.  The 
filament  of  carbon  always  broke  very  soon  at  its  center,  and,  in 
spite  of  the  efforts  of  inventors,  there  was  no  means  found  of 
preventing  it. 

M.  Emile  Reynier  was,  in  1877,  one  of  those  who  sought 
the  solution.  After  having  tried  different  means,  he  was  led 
to  think  that  if  the  pencil  touched  with  its  end  a  heavy  carbon, 
the  waste  would  not  take  place  in  the  middle  of  the  incandes- 
cent part  but  at  the  point  of  contact,  which  was  an  imperfect 
contact,  and  where  the  temperature  ought  to  be  the  highest. 

Experiments  verified  this  theoretical  view.  The  benefit  was 
double,  for  another  difficulty  of  the  problem,  that  of  the 
vacuum  in  the  interior  of  the  lamp,  was  solved,  or  rather 
avoided,  at  the  same  time  with  the  conservation  of  the  car- 
bons. As  the  consumption  of  carbon  took  place  gradually 
at  its  extremity,  it  became  useless  to  retard  this  combustion 
by  employing  a  closed  vessel ;  the  carbon  had  only  to  be 
pushed  forward  as  fast  as  used,  as  the  candles  in  carriage- 
lanterns  are. 

Still  further,  the  slow  combustion  of  the  incandescent  car- 
bon in  the  air  was  a  favorable  circumstance,  because  it  raised 
the  temperature,  and  consequently  augmented  the  luminous 
intensity.*  It  should  therefore  be  preserved  as  a  useful  ac- 
cessory. 

I.  THE  REYNIEE  LAMP. 

The  system  of  incandescence  in  open  air  was  thus  conceived. 
It  now  had  to  be  realized  in  a  practical  manner.  M.  Emile 
Reynier  immediately  devoted  himself  to  it. 

In  November  and  December,  1877,  he  began  the  construc- 
tion of  his  first  apparatus  in  the  laboratory  of  M.  Breguet ;  on 

*  [This  statement  is  very  frequently  made,  but  it  does  not  seem  to  be  war- 
ranted, as  the  combustion  of  such  a  minute  quantity  of  carbon  could  not  increase 
the  temperature  sufficiently  to  have  any  perceptible  influence  on  the  light.  The 
cooling  of  the  incandescent  carbon  by  the  air  would,  moreover,  much  more  than 
counterbalance  any  gain  from  combustion.] 


124: 


THE   INCANDESCENT  LIGHT. 


descence 
in  the 
open  air. 


February  19,  1878,  he  applied  for  a  patent,  and  on  May  13  he 
described  his  system  in  a  note  addressed  to  the  Academy  of 
Sciences  at  Paris,  in  which  he  gave  a  resume  of  the 
principle.     Fig.  74. 

If  a  thin  rod  of  carbon,  C,  pressed  laterally  by 
an  elastic  contact-piece,  Z,  and  pushed  in  the  line  of 
its  axis  upon  a  fixed  contact-piece,  B,  is  traversed 
by  a  sufficiently  powerful  current  between  these 
two  contacts,  it  becomes  incandescent  at  this  part 
of  its  length,  i  /,  and  burns  continuously,  grow- 
/Jik         ing  attenuated  toward  its  extremity.     As  the  end 
^ x         becomes  used  up,  the  rod,  continuously  pushed  on 
^Principle    ward,  advances,  rubbing  against  the  elastic  contact- 
of  incan-    piece,  so  as  always  to  rest  upon  the  stationary  con- 
tact-piece.    The  heat  developed  by  the  current  in 
the  carbon-rod  is  greatly  increased  by  the  combus- 
tion of  the  carbon. 

M.  Reynier  was  not  slow  to  recognize  the  fact  that  the 
fixed  immovable  carbon,  acting  as  contact- piece  for  the  incan- 
descent rod,  was  for  several  reasons  in- 
convenient. The  ash  accumulated  there, 
and  interfered  with  the  production  of 
the  light.  To  overcome  this  trouble  he 
made  the  piece  movable,  and  gave  it  the 
form  of  a  disk  turning  around  its  axis, 
analogous  to  that  which  had  been  em- 
ployed in  1845  for  the  voltaic  arc  by  an 
Englishman  named  Thomas  Wright.  On 
starting  out,  M.  Reynier,  for  turning  the 
carbon  disk,  used  a  mechanism  turning 
by  the  weight  of  the  upper  carbon-holder 
(Fig.  75).  But  he  was  not  slow  in  sim- 
plifying his  apparatus  in  a  most  ingen- 
ious manner,  producing  the  rotation  of 
the  disk  by  the  descent  of  the  carbon- 
rod  itself.  This  is  the  final  form  he 
adopted  for  his  lamp. 

The  carbon-rod  is  pushed  toward  the 
base  by  its  weight,  and  that  of  the  car- 
bon-holder, directed  by  rollers.  This 
rod  rests  on  a  carbon-disk,  a  little  in 
front  of  the  vertical  through  the  center  trode. 


INCANDESCENCE  IN  THE   OPEN  AIR. 


125 


of  the  disk.  The  descent  of  the  pencil,  resulting  from  its  con- 
sumption, thus  turns  the  disk  without  any  mechanism.  The 
rod  is  supported  at  a  short  distance  from  its  end  by  a  sleeve, 
and  below  this  comes  in  contact  with  another  carbon  contact- 
piece,  which  determines  the  length  of  its  incandescent  portion. 

By  a  very  simple  arrangement  the  pressure  exercised  by 
the  rod  upon  the  disk  is  transmitted  to  and  produces  an  auto- 
matic brake  action  up- 
on the  movable  carbon- 
holder  ;  it  follows  that 
its  weight  is  effectually 
sustained,  as  long  as  the 
carbon  is  long  enough 
to  bear  down  upon  the 
disk,  and  that  this 
weight  is  on  the  con- 
trary released  when  the 
lower  support  is  want- 
ing on  account  of  the 
consumption  of  the 
point. 

As  is  seen  in  the  im- 
age of  the  luminous  part 
of  this  lamp,  magnified 
and  projected  upon  a 
screen,  the  temperature  is  highest  at  the  lower  contact-point ; 
the  carbon,  grown  thin  by  slow  combustion  in  the  air,  sharp- 
ens itself  toward  its  base,  which  the  shape  and  motion  of  the 
pencil  facilitates. 

Finally,  to  prevent  the  incandescence  from  rising  too  far 
upward  on  the  pencil,  and  to  prevent  the  luminous  portion 
being  thus  extended,  it  is  touched  at  a  certain  distance  by 
another  carbon,  much  larger,  which  brings  the  current.  The 
incandescent  part  varies  thus  from  four  to  eight  millimetres, 
according  to  the  quantity  of  light  which  it  is  proposed  to  ob- 
tain, and  which  can  attain  five  to  twenty  Carcel  lamps,  provid- 
ed, of  course,  that  the  current  be  strong  enough. 


FIG.  76. — Magnified  image  of  the  incandescent  por- 
tion of  the  Reynier  lamp. 


II.  THE  WEKDERMANN  LAMP. 

While  M.  Reynier  was  occupied  in  France  in  perfecting 
his  incandescent  lamp,  an  Englishman,  Mr.  Richard  Werder- 


126 


THE   INCANDESCENT  LIGHT. 


maim,  was  working  in  London  upon  the  same  problem,  and 
he  there  took  out,  August  23,  1878,  a  patent  founded  on  the 
same  principles,  which  gave  rise  to  very  energetic  discussions 
between  the  two  engineers.  These  discussions  had  only  a 
theoretical  interest  for  them,  because  the  Jablochkoff  Com- 
pany, owner  of  the  Werdermann  patents, 
bought  the  Reynier  patents,  and  it  is  this 
company  which  has  especially  contributed 
to  fix  upon  the  incandescent  lamps  the 
name  of  Werdermann  lamps,  although  the 
principle  at  least,  if  not  the  actual  arrange- 
ments, belong  probably  to  M.  Reynier. 

One  of  the  innovations  introduced  by 
Mr.  Werdermann  consisted  in  the  inver- 
sion of  the  apparatus.  The  large  disk 
placed  at  the  base  of  his  apparatus  by 
M.  Reynier  cast  disagreeable  shadows. 
Mr.  Werdermann  placed  it  above,  and 
pushes  up  his  carbon-rod  by  means  of  a 
counterpoise  (Fig.  77). 

In  the  Reynier- Werdermann  lamp  it 
is  less  a  true  incandescence  that  is  pro- 
duced than  a  sort  of  voltaic  arc,  very 
short,  combined  with  incandescence  of 
the  electrodes,  and  Mr.  Werdermann  has 
noted  in  his  experiments  some  very  curi- 
ous deformations  of  electrodes  of  differ- 
ent sizes  under  the  effect  of  the  voltaic 


FIG.  77. — Werdermann 
lamp. 

C,  disk  of  carbon  support- 
ed by  the  arm  D. 

T,  tube  serving  to  guide 
the  carbon  rod  B. 

K,  spring,  with  regulating 
screw  for  limiting  the 
action  of  the  counter- 
poise. 


arc. 


a  cord  passing  over  pul- 
leys to  advance  the  rod 
B. 


When  the  voltaic  arc  is  produced  be- 
tween two  carbons  of  the  same  section, 
the  changes  of  their  polar  extremities  are 

E,     counterpoise     acting 

through  the  medium  of  produced  in  the  manner  already  known  ; 
the  positive  electrode,  heated  to  a  white 
heat,  takes  the  shape  of  a  mushroom,  hol- 
lows itself  into  a  cup,  and  is  used  up 
twice  as  rapidly  as  the  negative  electrode.  The  latter,  which 
is  only  heated  to  redness  by  the  current,  is  slowly  formed 
into  a  point,  and  the  length  of  the  arc  is  in  proportion  to  the 
tension  of  the  current. 

The  result  is  altogether  different  if  different  sections  be 
given  to  the  two  electrodes.    When  the  section  of  the  positive 


INCANDESCENCE, IN  THE  OPEN  AIR.  127 

electrode  is  gradually  diminished,  and  that  of  the  negative 
electrode  is  increased,  the  red  heat  observable  at  the  end  of  the 
latter  is  gradually  diminished,  while  the  heat  of  the  positive 
electrode  increases  in  proportion  to  the  reduction  of  its  section. 
The  electric  current  does  not  pass  across  the  space  intervening 
between  the  electrodes  with  the  same  facility,  and  to  succeed 
in  maintaining  the  voltaic  arc  the  electrodes  must  be  brought 
closer  together,  so  that  the  current  can  pass  over  the  dimin- 
ished distance  between  them. 

At  this  point  a  strange  phenomenon  becomes  manifest :  the 
end  of  the  positive  electrode  increases  considerably  in  size,  and 
the  current  shows  a  tendency  to  equalize  the  two  surfaces — 
that  is  to  say,  to  give  to  the  positive  electrode,  as  far  as  may 
be,  the  same  section  as  that  of  the  negative.  The  greater  the 
difference  between  the  sections  of  the  electrodes,  the  smaller 
must  the  distance  between  them  be,  and  to  avoid  too  great  an 
increase  in  the  size  of  the  positive  electrode  the  tension  of  the 
current  must  be  somewhat  reduced,  which  is  easily  managed 
by  employing  a  Gramme  machine,  with  which  the  tension  of 
the  current  is  proportional  to  its  velocity,  the  resistance  of  its 
armature  remaining  constant. 

A  limit  is  thus  reached  when  the  distance  between  the  elec- 
trodes becomes  infinitely  small — that  is  to  say,  when  the  elec- 
trodes are  in  contact.  It  is  when  their  sections  are  in  the  ratio 
of  1  to  64  ;  then  the  negative  electrode  is  hardly  heated  at  all, 
and  consequently  is  not  consumed.  In  these  conditions  the 
positive  electrode  only  is  the  one  that  burns,  producing  a  beau- 
tiful light,  absolutely  fixed,  and  lasting  as  long  as  close  con- 
tact between  it  and  the  negative  electrode  is  maintained.  In 
reality,  then,  it  is  an  incandescent  light,  increased  by  the 
presence  of  an  infinitely  small  voltaic  arc,  which  keeps  the 
consumption  of  the  carbon  confined  to  its  point.  If  the  pressure 
is  strong  enough  to  make  the  contact  too  complete,  the  com- 
bustion will  be  retarded  a  little,  the  carbon  will  be  detached  in 
fragments,  and  the  light  will  no  longer  possess  the  steadiness 
which  is  its  most  desirable  quality. 

When  the  operation  is  reversed— that  is  to  say,  when,  in- 
stead of  diminishing  the  section  of  the  positive  electrode,  the 
section  of  the  negative  electrode  is  diminished  step  by  step, 
and  that  of  the  positive  electrode  is  at  the  same  time  increased, 
the  light  of  the  latter  is  diminished  little  by  little,  and  the 
temperature  of  the  negative  electrode  increased. 
10 


128 


THE  INCANDESCENT  LIGHT. 


When  the  sections  of  the  electrodes  are  in  the  ratio  of  1  to 
64,  and  when  they  can  be  brought  into  contact,  no  light  is 
emitted  by  the  positive  electrode,  but  only  by  the  negative. 
What  is  curious  is  that  when  a  voltaic  arc  is  started  between 
the  two  carbons,  the  smaller  electrode  always  becomes  pointed, 
whether  positive  or  negative. 


FIG.  78.— Burner  of  the  Key  nier  lamp.  FIG.  79.— Keynier's  incandescent  lamp  with 

globe. 

C,  movable  rod  of  carbon. 
B,  contact  block  of  graphite. 

L,  lateral  contact  piece  made  of  a  block  of  graphite  fastened  into  a  tube  pivoted  into  the  sup- 
porting arm. 

K.  spring  maintaining  the  lateral  contact  pressure. 
I  J,  luminous  part. 


III.  THE  ACTUAL  REYNIER-WERDERMANN  LAMPS. 

During  nearly  two  years  in  which  it  has  been  operated  the 
Reynier-Werdermann  lamp  has  undergone  several  changes  in 
its  accessory  parts,  especially  in  those  which  press  the  rod  of 
incandescent  carbon  against  the  abutting  disk.  M.  Trouve, 
M.  Ducretet,  M.  Tommasi,  have  suggested  various  modifica- 
tions, some  of  which  already  figure  in  the  work  of  M.  Reynier ; 


INCANDESCENCE  IN  THE  OPEN  AIR. 


120 


and  M.  Napoli,  engineer  of  the  company  owning  the  Reynier- 
Werdermann  lamp,  inspired  by  the  inventor's  ideas,  has  given 
to  the  apparatus  the  general  arrangement  of  parts  that  it  pos- 
sessed as  exhibited  in  the  Electrical  Exhibition  at  Paris. 

M.  Reynier  himself  has  succeeded  in  further  simplifying 
his  former  arrangements  so  as  to  obtain  better  coniacter-aoid  to 


FIG.  80. — Chandelier  of  Werdermann  lamps. 

diminish  shadows,  thanks  to  the  substitution  of  graphite  for 
carbon  as  contact-pieces.  To-day  he  uses  a  new  burner,  whose 
construction  is  shown  in  Fig.  78.  This  burner  can  easily  be  con- 
tained within  a  globe,  and  constitutes  a  very  simple  lamp,  like 
that  shown  in  Fig.  79. 


130 


THE  INCANDESCENT  LIGHT. 


The  rods  actually  employed  have  a  diameter  of  two  milli- 
metres and  a  half,  and  are  one  metre  long.  They  last  six 
hours. 

Eleven  of  these  lamps,  in  nse  in  a  cloth-bleaching  estab- 
lishment at  Lisieux,  and  supplied  by  a  Gramme  machine, 
work-shop  type  (type  (Tatelief),  required  three  horse  power. 
Each  burner  had  an  intensity  varying  from 
eight  to  twelve  Carcels,  according  to  the  speed 
of  the  machine. 

The  English  Joel  lamp  is  not  essentially  dif- 
iferent  from  the  Reynier-Werdermann  lamps. 
Continuous  currents  are  used  for  this  kind 
of  incandescent  lighting,  and  the  lamps  can 
work  not  only  with  dynamo-electric  machines 
but  also  with  batteries  ;  eight  Bunsen  elements 
are  enough  to  give  a  light  of  about  four  Car- 
cels, which  is  an  invaluable  feature  as  regards 
laboratory  work. 

For  equal  production  of  light,  incandescent 
lighting  in  open  air  costs  certainly  more  than 
voltaic-arc  illumination ;  but  it  makes  possi- 
ble the  subdivision  of  the  light  into  centers  of 
smaller  intensity,  while  the  regulator  voltaic- 
arc  lights  must  be  much  stronger  to  give  good 
results. 

This  subdivision  permits  us  to  distribute  in 
a  much  more  even  manner,  and  consequently 
to  better  utilize,  the  light  produced,  while  the 
great  lights  illuminate  too  strongly  objects  in 
their  immediate  vicinity,  and  not  enough  at  the 
limiting  distance  of  their  action.  Moreover, 
these  powerful  lights  need  protecting  opaline 
globes,  which  often  cut  off  a  third  of  the  light 
produced,  and  sometimes  more.  Finally,  the 
incandescent  light  is  milder  than  the  voltaic- 
arc  light ;  it  has  no  bluish  tints,  due  to  little  flames  of  car- 
bonic oxide,  which  give  so  cold  an  aspect  to  regulators  as 
well  as  to  candles  ;  its  rays,  slightly  yellow,  do  not  offend  the 
eye,  and  do  not  subject  it  to  the  influence  of  rays  of  colors  it 
is  unaccustomed  to. 

It  is  also  the  only  one  which  not  only  permits  extinction 
and  relighting  of  the  light  at  will,  like  regulators,  but  also 


FJG.  81.— Reynier's 
latest  form  of  in- 
candescent lamp. 


INCANDESCENCE  IN  THE   OPEN  AIR. 


131 


the  varying  of  intensity  to  a  great  extent,  by  introducing  into 
the  circuit  suitable  resistances. 

The  Reynier-Werdermann  lamps  to-day  can  be  used  almost 
to  as  great  advantage  as 
vacuum  incandescent 
burners  in  the  decorative 
fixtures  of  rooms.  They 
construct  especially  with 
them  lusters  of  ten  jets 
(Fig.  80),  which  light 
up  large  saloons  with 
as  much  effulgence  as 
immense  candle-chande- 
liers, but  with  much  high- 
er luminous  intensity. 

For  all  these  reasons, 
the  success  of  open-air 
incandescent  lamps  has 

been  Very  great,  especial-  FlG-  82.—  Eeymer  automatic  lighter. 

ly  in    London,  and   all 

believe  that  their  use  will  be  continued  although  they  have 

been  little  employed  in  Paris  up  to  the  present  day. 

[Quite  recently  M.  Rey- 
nier  has  devised  another 
form  of  open-air  incandes- 
cent lamp  which  is  free 
from  the  objections  to  the 
above  lamp,  and  which  is, 
if  anything,  simpler  in  con- 
struction. In  the  lamp  de- 
scribed, the  contact  which 
formed  the  upper  limit  to 
the  incandescence  of  the 
pencil  lowered  the  econo- 
my of  the  lamp  by  con- 
ducting away  a  part  of 
the  heat,  and  the  feeding 
of  the  pencil  through  this 
contact  was  not  wholly  sat- 
isfactory. In  the  later  lamp,  two  carbon  pencils  are  used, 
slightly  inclined  to  each  other,  so  that  they  touch  at  a  short 
distance  from  their  points,  which  rest  upon  small  abutments 


"* 


132  THE  INCANDESCENT  LIGHT. 

of  copper.  The  relation  of  the  parts  is  shown  in  Fig.  81. 
The  carbons  A,  B,  are  pressed  downward  by  the  weights 
P,  Q,  sliding  upon  the  metallic  guides  C,  D.  The  points  of 
these  carbons  rest  upon  the  copper  abutments  E,  F,  attached 
to  the  curved  metallic  bars  G,  H.  The  current  enters  at  the 
terminal  K,  follows  the  rod  C,  the  arm  G,  and  abutment  E, 
to  the  point  of  the  carbon  resting  upon  it.  It  then  passes  up 
this  carbon  to  the  point  x,  at  which  the  two  carbon-rods 
touch,  then  across  to  the  other  carbon  and  downward,  out  to 


FIG.  84. — Reynier  system  of  distribution. 

the  terminal  L,  by  a  similar  route  taken  on  entering.  The 
contact  limiting  the  incandescence,  it  will  be  seen,  is  a  hot 
contact,  and  hence  this  arrangement  should  be  a  more  eco- 
nomical one  than  that  of  the  former  lamp.] 

IV.   INSTALLATION  OF  REYNIER-WERDERMANN  LAMPS. 

For  lamps  of  this  system  M.  Reynier  has  invented  his  auto- 
matic lighter  (Figs.  82,  83),  which  performs  almost  the  same 
office  as  the  safety-box  of  M.  de  Mersanne  does  for  regulators. 

The  most  usual  system  of  distribution  consists  in  placing 
the  lamps  one  after  the  other  on  the  same  circuit ;  but  then  if 
one  of  them  goes  out  on  account  of  the  breakage  or  exhaus- 
tion of  a  carbon,  all  the  others  will  go  out  at  the  same  time. 
This  the  lighter  is  designed  to  prevent,  by  substituting  for 


INCANDESCENCE  IN  THE  OPEN  AIR. 


133 


the  extinguished  lamp  a  resistance  which  is  ordinarily  formed 
by  a  wire  of  German  silver.    • 

The  apparatus  is  provided  with  an  electro-magnet  placed 
in  the  main  circuit  C  C  (Fig.  83) ;  while 
the  lamp  is  working,  the  armature  is  at- 
tracted, and  the  auxiliary  resistance-coil 
R  is  cut  out  of  the  circuit ;  when  the 
lamp  goes  out,  the  electro-magnet  be- 
comes inactive,  the  armature  drops  back 
under  the  influence  of  its  spring,  and 
effects  a  contact,  at  E  (Fig.  82),  between 
the  two  ends  of  the  auxiliary  circuit.  The 
current  passes  through  the  resistance-coil 
R,  and  as  this  represents  exactly  the 
value  of  a  lamp  burning,  the  other  appa- 
ratus on  the  same  circuit  are  not  affected. 
As  soon  as  the  lamp  is  restored  to  its 
normal  working  condition,  the  current 
again  passes  in  its  regular  course,  every- 
thing resumes  its  place  and  the  lighter 
returns  to  duty.  Of  course  there  must 
be  a  lighter  for  each  lamp  ;  but  the  re- 
sistance-coil can  be  replaced  by  a  second 
lamp  which  burns  as  long  as  the  first  one 
is  extinguished,  so  that  the  service  expe- 
riences neither  interruption  nor  diminu- 
tion. Fig.  84  explains  how  a  series  of 
lamps  can  be  arranged.  Three  lamps, 
L, ,  L/,  L,",  are  mounted  in  series  on  the 
circuit,  Pp  NT&,  of  a  battery,  E ;  they 
are  respectively  in  connection  with  three 
automatic  lighters,  M,  M',  M",  whose 
contacts  are  at  c  c'  c" .  Each  lamp  has 
a  second  resistance  or  a  second  lamp, 
La  L2'  L2". 

To  replace  the  German-silver  coil,  and 
as  substitute  for  these  lamps,  M.  Rey- 
nier  sometimes  uses  a  little  regulator, 
which  will  work  long  enough  to  permit  the  lamp  to  be  resup- 
plied  with  carbon,  without  interrupting  the  lighting.     This 
very  simple  apparatus  is  composed  of  a  solenoid  (Fig.  85),  a 
soft  iron  rod,  and  a  spring.    The  upper  carbon  is  fixed  ;  the 


FIG.  85.— Temporary  regu- 
lator of  Keynier,  serving 
as  a  safety-lamp,  in  elec- 
tric installations. 


134 


THE  INCANDESCENT  LIGHT. 


lower  carbon  is  carried  by  the  rod  of  soft  iron  and  follows  its 
movements.  The  spring  is  adjusted  to  balance  the  attraction 
of  the  solenoid  in  all  positions  of  the  rod,  as  long  as  the  cur- 
rent possesses  normal  intensity.  If  the  intensity  increases, 
the  rod  is  attracted  ;  if  it  diminishes,  the  spring  acts  ;  the 
length  of  the  arc  remains  constant.  Although  supplied  with 
a  button  to  regulate  the  tension  of  the  spring,  this  lamp  can 
only  work  within  very  narrow  limits  of  intensity  of  the  cur- 
rent. It  is  only  a  safety  lamp. 


FIG.  86. — Incandescent  lamp  with  rota- 
ting electrode,  of  M.  Ducretet. 


FIG.  87.— Incandescent  lamp  of  M. 
Ducretet. 


Y.   VARIOUS  LAMPS. 

The  labors  of  M.  Eeynier  have  produced  several  models  of 
lamps  which  it  is  interesting  to  study,  although  they  may  not 
have  entered  the  domain  of  every-day  use. 

M.  Ducretet  has  taken  up  again  Harrison's  lamp,  and  has 
adapted  to  it  a  mechanism  which  at  the  same  time  regulates 
the  descent  of  the  carbon-rod  and  the  rotation  of  the  abut- 


INCANDESCENCE  IN  THE  OPEN  AIR. 


135 


ting-disk.  In  Fig.  86  it  will  be  seen  that  the  rod  is  pressed 
from  above  downward  by  a  weight,  J,  and  that  toward  the 
base  it  passes  through  another  block,  Z,  which  acts  as  guide, 
and  also  limits  the  length  of  the  incandescent  part.  The  de- 
scent is  restrained  by  a  cord,  ^,  wound  upon  a  small  drum  ; 
a  second  cord  transmits  to  the  disk  a  movement  of  rotation. 
Two  small  electro-magnets  with  fine  wire  are  placed  in  de- 
rived circuit ;  one,  E',  acts  to  regulate  the  movement  of  the 


FIG.  88.— Section  of  M.  Ducretet's  lamp. 


E.UUCRETET  &  Cli 


FIG.  89.-^M.  diamond's  incandescent  lamp. 


machinery  ;  the  other,  E,  to  arrest  it  completely  when  the 
carbon-rod  is  used  up. 

By  this  apparatus  the  contact  can  be  modified  at  will,  and 
even  can  be  suppressed  entirely  by  maintaining  constantly  a 
small  distance  between  the  carbon  and  the  disk.  Six  Bunsen 
elements  are  enough  to  give  a  voltaic  arc. 

In  another  model  M.  Ducretet  has  put  into  practice  an 
idea  formerly  enunciated  by  M.  Reynier.  The  carbon-rod  is 
pushed  from  above  downward  by  the  hydrostatic  pressure  of 


136 


THE  INCANDESCENT  LIGHT. 


a  column  of  mercury  sealed  up  in  an  iron  tube  which,  acts  as 
standard  for  the  lamp.  Figs.  87  and  88  show  the  exterior 
view  and  vertical  section  of  this  lamp.  They  are  so  easy  to 

understand  as  to  need  no  ex- 
planation. 

M.  Clamond  has  invented  a 
small  incandescent  lamp  (Fig. 
89),  in  which  the  rod  of  carbon, 
C,  descends  freely  through  a 
hollow  iron  guide,  B,  con- 
taining a  little  mercury,  m. 
The  rod  fills  the  hole  closely 
enough  to  prevent  the  mer- 
cury from  running  out ;  it  also 
secures  a  good  contact  for  the 
passage  of  the  current.  This 
would  seem  to  be  a  very  con- 
venient apparatus  for  labora- 
tory use. 

[A  lamp  of  the  same  type 
as  the  Reynier-Werdermann, 
but  in  which  the  incandes- 
cence takes  place  in  an  atmos- 
phere of  nitrogen,  was  con- 
structed in  the  United  States 
by  Sawyer  and  Mann.  One 
form  of  it  is  shown  in  Fig. 
90.  The  pencil  is  fed  up- 
ward, through  an  elastic  con- 
tact, to  a  pair  of  grooved  roll- 
ers which  form  the  abutment. 
The  mechanism  of  the  lamp  is 
inclosed  in  a  glass  bell,  joined 
to  a  metal  base,  from  which 
the  air  has  been  exhausted 
and  replaced  with  pure  nitro- 
gen. In  the  latest  form  of  this  lamp  the  abutment  is  a  block 
of  carbon  instead  of  the  rollers,  and  a  mechanism  operated 
by  a  coiled  spring  is  substituted  for  the  electro-magnetic 
device  previously  used.] 


FIG.  90. — Sawyer's  incandescent  lamp  in  an 
atmosphere  of  nitrogen. 


THE   SUN-LAMP.  137 

CHAPTER  III. 

THE  SUN-LAMP. 

IN  the  classification  of  electric  lamps,  the  sun-lamp  occu- 
pies an  altogether  separate  position,  and  a  very  difficult  one 
to  define  in  a  word.  It  is  a  voltaic-arc  lamp,  and  yet  the  vol- 
taic arc,  being  only  utilized  as  a  source  of  heat,  has  not  the 
usual  inconveniences  ;  it  is  also  an  incandescent  lamp,  because 
the  light  comes  from  an  incandescent,  solid,  refractory  sub- 
stance;  but  this  •  material  does  nofc  act  in  any  sense  as  con- 
ductor for  the  electric  current ;  the  voltaic  arc  heats  it,  and 
thus  make  it  luminous. 

Finally,  it  must  be  remarked  that,  above  all  it  is  a  lamp 
without  mechanism,  the  same  as  candles  and  incandescent 
lamps  for  open  air  or  in  sealed  vessels. 

I. 

The  Jablochkoff  candle  was  the  starting-point  in  the  in- 
vention of  the  sun-lamp.  The  earlier  of  the  two  inventors 
of  this  lamp,  M.  Clerc,  was  engineer  of  the  Jablochkoff  Com- 
pany, and  as  such  had  to  follow  day  by  day  the  practical 
working  of  all  the  parts  of  the  candle.  Like  many  others,  he 
had  doubts  of  the  true  office  and  utility  of  the  colombin  which 
separated  the  two  carbon-rods.  It  was,  moreover,  at  this 
period  an  insulating  rod  of  kaolin,  which,  it  was  said,  while 
preventing  all  passage  of  electricity  while  cold,  became  to  some 
extent  a  conductor  when  heated  between  the  two  points,  and 
thus  permitted  the  formation  of  a  derived  current  through  the 
length  of  this  layer  of  melted  porcelain. 

But  from  the  moment  when  plaster  was  substituted  for 
porcelain  in  the  construction  of  the  insulating  colombin,  this 
explanation  could  not  hold,  because  this  new  colombin  did 
not  melt,  and  was  a  non-conductor  when  cold.  To  ascer- 
tain its  true  function,  M.  Clerc  tried  candles  without  a  co- 
lombin, and  found  that  they  were  subject  to  still  more 
frequent  extinctions.  What  was  the  reason  of  these  extinc- 
tions ? 

Examining  these  candles  without  a  colombin,  it  was  seen 
that  the  arc  oscillated  between  the  points,  often  left  them  and 


138  THE  INCANDESCENT  LIGHT. 

descended  toward  the  base  of  the  cones,  where  the  distance  be- 
tween the  carbonaceous  rods  was  less,  and  where  the  disinte- 
gration of  the  carbon  caused  the  accumulation  of  some  dust, 
which  seemed  to  attract  it. 

The  arc  seemed  to  lick  this  dust,  and  thus  maintain  itself 
for  more  or  less  time  at  the  base  of  the  cones.  If  it  only 
deserted  the  points  for  one  or  two  seconds  there  was  no 
extinction ;  if  it  was  longer  absent,  extinction  was  cer- 
tain, the  cold  points  offering  then  too  great  a  resistance 
to  the  formation  of  the  arc  when  this  tended  to  mount 
upward  again  toward  them.  Hence  it  is  evident  that  it  is 
necessary  to  keep  the  points  warm,  if  extinctions  are  to  be 
avoided. 

The  role  of  the  colombin  becomes,  then,  easy  to  explain. 
It  opposes  the  descent  of  the  arc  and  prevents  it  from  aban- 
doning the  points  for  any  length  of  time,  and  thus  prevents 
extinctions.  We  have  seen  that  in  the  ordinary  candles,  if 
the  arc  hollows  out  in  any  way  the  colombin,  it  may  abandon 
the  points,  and  that  then  extinction  becomes  probable. 

The  Jablochkoff  candle,  then,  has  in  itself  a  cause  of  ex- 
tinction, which  is  but  the  exaggeration  of  that  which  pro- 
duces the  excessive  variations  in  the  light,  and,  to  overcome 
this  cause  of  extinction,  it  is  necessary  to  employ  a  material 
not  only  refractory  at  ordinary  heat,  but  also  capable  of  with- 
standing the  strains  due  to  the  voltaic  arc. 

Having  gone  so  far,  M.  Clerc  might  have  found  in  the  re- 
searches of  M.  Leroux,  tutor  at  the  Ecole  Poly  technique,  which 
researches  he  may  not  have  been  familiar  with,  the  indications 
of  the  way  to  pursue  to  find  the  solution. 

In  1868,  long  before  the  Jablochkoff  candle,  M.  Leroux 
had  noticed  the  advantages  of  a  refractory  material  in  such 
cases.  He  announced  that  if  there  was  placed  in  the  neigh- 
borhood of  the  arc,  on  the  side  opposite  to  that  where  the 
light  was  to  be  utilized,  a  body  capable  of  returning  in  the 
form  of  light  the  enormous  flow  of  calorific  radiations  which 
the  carbons  and  arc  set  free,  these  radiations  would  be  better 
utilized  than  by  any  other  process.  At  the  same  time  the 
arc  would  be  protected  by  a  sort  of  screen  which  would 
annul  in  almost  a  complete  hemisphere  all  the  causes  of  de- 
rangement produced  by  the  incessant  shif tings  of  the  arc, 
whose  point  of  departure  is  very  uncertain. 

To  fulfill  this  function,  it  became  necessary  to  choose  a 


THE  SUN-LAMP.  139 

body  at  once  a  poor  conductor  of  heat,  and  of  light  radiating 
power — conditions  which  lime,  magnesia,  and  in  general  the 
earthy  oxides,  fulfill  to  a  high  degree. 

M.  Leroux  first  tried  experiments  with  cylinders  of  mag- 
nesia, compressed  according  to  Carron's  system  and  manu- 
factured for  oxyhydic  illumination.  If  we  place  the  base  of 
one  of  these  cylinders,  whose  diameter  is  about  eight  milli- 
metres, at  a  very  small  distance  from  the  carbon-points  of 
an  electric  lamp,  so  that  the  magnesia  will  be,  as  it  were, 
licked  by  the  voltaic  arc,  this  will  become  incandescent  to 
a  degree  comparable  to  that  of  the  most  luminous  part  of 
the  carbons. 

At  the  same  time  the  light  acquires  a  remarkable  constan- 
cy, due  to  the  fixity  of  the  arc.  M.  Leroux  could  even  give  to 
the  latter  more  length  than  was  usual,  because  the  mass  of 
magnesia  acted  as  a  screen  and  maintained  in  this  location  the 
elevation  of  temperature,  so  that  the  danger  of  rupture  of  the 
arc  became  much  reduced. 

The  magnesia  can  also  be  kept  in  the  voltaic  arc  for  more 
than  an  hour  before  the  surface  will  become  sufficiently 
changed  to  vary  the  conditions  of  the  experiment ;  during  the 
first  few  moments  its  surface  will  be  hollowed  out,  but  if  the 
pencil  of  magnesia  is  kept  stationary,  the  action  of  the  arc 
growing  weaker  at  a  short  distance  it  ceases  to  waste  away. 
It  undergoes,  it  is  true,  an  alteration  of  another  kind  :  it  ab- 
sorbs the  silicious  vapors  which  the  voltaic  arc  carries,  and 
forms  with  them  a  sort  of  glass,  slightly  green  when  cold  and 
very  hard.  This  circumstance  is  attended  with  the  inconven- 
ience of  greatly  diminishing  the  radiating  power  of  the  mag- 
nesia, and  this  new  experiment  shows  again  how  necessary 
it  is  to  have  an  industrial  manufacture  of  pure  carbon  in  a 
proper  condition  for  the  production  of  the  electric  light. 

4 'The  voltaic  arc,"  said  M.  Leroux,  in  describing  his  ex- 
periments, "  playing  between  two  pencils  of  pure  carbon  in  the 
recess  of  a  cavity  of  magnesia  or  other  alkaline  earth,  would 
certainly  be  one  of  the  most  beautiful  sources  of  light  that  it 
is  possible  to  realize." 

But  M.  Leroux  did  not  try  to  practically  utilize  the  result 
that  theory  had  made  him  foresee,  and  it  was  no  less  than 
eleven  years  later  that  M.  Clerc  was  logically  brought  to  the 
same  conclusion  again  by  the  line  of  research  that  we  have 
just  described. 


140  THE  INCANDESCENT  LIGHT. 

II. 

M.  Clerc  made  the  two  rods  of  carbon,  that  formed  essen- 
tially the  Jablochkoff  candle,  abut  upon  a  block  of  lime,  and 
the  arc  playing  across  this  block  was  not  extinguished. 

But  the  arc  shifted  about,  and  gave  always  a  flickering 
light.  To  fix  it,  M.  Clerc  conceived  the  idea  of  placing 
against  the  carbons,  and  perpendicularly  to  the  block,  two 
thin  plates  of  lime,  provided  only  with  a  small  slit  through 
which  the  arc  could  pass.  The  arc  was  guided,  in  fact,  and  in 
consequence  the  light  became  absolutely  fixed. 

Nevertheless,  it  was  far  from  perfect,  for  it  had  still  the 
violet  tints  due  to  the  presence  of  carbonic  oxide  vapors, 
which  tints  the  radiation  from  the  block  of  lime  could  not 
whiten  because  it  was  not  yet  hot  enough.  By  enclosing  the 
two  points  in  a  block  of  refractory  material  provided  with 
two  slits  destined  for  the  passage  of  the  voltaic  arc,  M.  Clerc 
succeeded  in  concentrating  the  heat  of  the  carbon-poles,  and 
while  diminishing  their  consumption  in  raising  still  higher 
the  temperature  of  the  block  ;  the  light  also  changed  its  color 
and  assumed  a  slightly  golden  tint,  like  that  of  the  sun,  which 
gave  the  lamp  the  name  it  has  to-day. 

In  spite  of  the  importance  of  these  results,  the  sun-lamp 
was  lacking  in  a  condition  more  indispensable  than  all  the 
others.  However  beautiful  it  might  be,  its  light  did  not  last. 
At  the  end  of  an  hour  the  voltaic  arc  became  buried  in  the 
refractory  material,  and  the  light  was  lost  along  with  it  in  the 
cavern  it  had  cut  out.  Other  materials  tried  in  place  of  lime 
resisted  no  better,  and  the  misfortune  seemed  irreparable.  Its 
cause  was  this : 

When  the  voltaic  arc  is  started  between  two  carbon-points, 
horizontal  or  inclined  one  toward  the  other,  it  bends  and 
takes,  under  the  influence  of  the  ascending  currents  of  air,  the 
curved  form  that  gave  it  its  name.  If  the  refractory  block, 
which  is  cold,  be  brought  near  it,  the  arc  is  then  repelled,  and 
is  bent  in  the  opposite  direction  ;  but  the  material  soon  grows 
hot,  and,  at  the  end  of  a  certain  period,  the  arc  reassumes  its 
original  curved  form,  cutting  a  passage  for  itself  in  the  block 
of  refractory  material.  The  light  disappears  then  almost  en- 
tirely. 

Some  arrangement  must  be  sought  for  that  will  prevent  it 
burying  itself  in  this  cavity.  M.  Clerc  removed  the  trouble 


THE  SUN-LAMP. 


141 


by  sliding  the  two  carbon-rods  through  two  holes,  bored 
through  the  middle  of  the  refractory  mass,  so  that  only  their 
points  project.  The  voltaic  arc  is  produced  between  these 
two  points,  licks  the  face  of  the  material  with  its  interior  face, 
instead  of  its  exterior  face  as 
before,  and  the  chrysalis  was 
at  full  liberty  to  develop  itself 
into  a  butterfly. 

At  the  same  time  the  heat 
of  the  blue  carbon  monoxide 
vapor  was  utilized  in  heating 
the  refractory  material,  where 
it  produced  a  vitrified  surface, 
such  as  that  described  by  M. 
Leroux.  Finally,  the  appara- 
tus which  formerly  faced  up- 
ward, now  cast  its  light  down- 
ward, generally  the  only  part 
to  be  lighted  ;  in  all  these 
cases  it  threw  it  entirely  in 
a  single  direction,  which  of 
course  could  be  changed  at 
will. 

A  proper  refractory  mate- 
rial now  had  to  be  chosen, 
which  required  a  large  num- 
ber of  experiments  and  differ- 
ent trials.  To  execute  them, 
M.  Clerc,  who  was  engaged  in 
establishing  electric  lights  on 

the  candle  system  in  several  cities  of  Belgium,  associated  with 
himself  one  of  his  friends,  M.  Bureau,  engineer  of  the  con- 
struction works  of  M.  Carels,  at  Gand,  who  eventually  gave 
the  lamp  a  final  practical  form  and  arrangement. 


YiGr.  91. — Vertical  section  of  the  lamp- 
soleil. 

C,  C,  carbon-rods  receiving  the  current  by 
the  wires  shown — above,  at  C,  the  shape 
of  the  cross-section  is  given. 

B,  block  of  marble  or  compressed  magnesia, 
the  lower  face  of  which  becomes  incan- 
descent. 

A,  A,  cast-iron  box  holding  the  pieces  of  re- 
fractory stone  which  form  the  protect- 
ing screen  of  the  lamp. 

D,  small  strip  of  plumbago  or  carbon  con- 
necting the  tips  of  the  carbon-rods,  to 
light  the  lamp. 


III. 

At  the  beginning  of  the  year  1880,  then,  the  sun-lamp  was 
essentially  completed  in  all  its  parts,  as  we  see  it  to-day  (Fig. 
91).  It  would  be  difficult  to  find  anything  simpler  and  less 
delicate. 

It  comprises  two  semi-cylindrical  rods  of  carbon,    two 


THE  INCANDESCENT  LIGHT. 

centimetres  in  diameter,  inclined  at  an  angle  of  about  15° 
toward  each  other,  and  separated  by  a  small  block  of  com- 
pressed magnesia  or  of  marble,  into  which  they  are  forced 
down  to  a  small  cavity  made  in  the  lower  face  of  the  block— 
a  cavity  in  which  the  voltaic  arc  is  produced.  Pieces  of  re- 
fractory stone  inclosed  in  a  cast-iron  box  form  a  protecting 
screen  around  the  whole  apparatus,  and  may  be  as  large  as 
desired,  as  they  can  cause  no  imaginable  inconvenience  since 
they  cast  no  shadow  below.  Finally,  a  strip  of  plumbago 
unites  the  two  points  of  the  carbon-rods  to  cause  the  first  pas- 
sage of  the  current  and  consequent  lighting  of  the  lamp. 

The  steadiness  which  is  the  great  object  sought  for  in  vol- 
taic lamps  was  here  attained  almost  in  perfection.  In  a  word, 
the  principal  cause  of  the  variations  of  the  electric  light  is 
the  instability  of  the  arc,  which  at  every  instant  changes  the 
point  where  it  leaves,  or  springs  from  the  carbon  electrodes, 
and  consequently  its  path  through  the  air.  Hence  come  the 
alternations  of  light  and  weakened  intensity,  as  well  as  the 
changes  in  color  from  red  to  blue.  In  the  sun-lamp  the  arc 
can  change  just  as  freely  its  point  of  departure  from  the  car- 
bons ;  but  it  has  to  pass  through  the  only  path  that  is  open 
to  it  through  the  refractory  material.  This  gives  it  an  abso- 
lutely fixed  and  invariable  position. 

A  second  cause  of  fixity  is  due  to  the  fact  that  the  greater 
part  of  the  light  is  due  to  a  refractory  body  in  a  state  of  in- 
candescence under  the  influence  of  the  enormous  temperature 
of  the  arc.  For,  if  the  intensity  of  the  current  varies  for  any 
reason,  these  variations  do  not  manifest  themselves  rapidly 
nor  in  a  very  sensible  manner,  for  the  temperature  of  the  in- 
candescent medium  can  not  vary  quickly,  and  it  is  this  incan- 
descence which  produces  the  light.  It  constitutes  as  it  were 
a  fly-wheel,  to  borrow  a  mechanical  metaphor,  and  regulates 
the  emission  of  light  by  the  quantity  of  heat  which  it  keeps 
stored  up  ready  to  be  restored  to  the  arc  at  the  proper  mo- 
ment. From  another  point  of  view,  in  all  the  arc  systems  the 
light  is  given  by  the  points  of  the  carbons,  and  it  contains 
many  blue  and  violet  rays.  It  is  these  rays,  and  the  continual 
and  sudden  variations  in  intensity,  which  are  the  cause  of  its 
injurious  action  on  the  eye — an  action  so  often  and  sometimes 
so  justly  complained  of  in  the  electric  light.  In  the  sun-lamps, 
the  carbons  being  completely  hidden  in  the  midst  of  the  refrac- 
tory material,  their  points  are  invisible. 


THE   SUN-LAMP. 


143 


Finally,  the  block  as  it  is  used  drops  a  certain  amount  of 
dust,  which,  after  a  certain  time,  soils  the  globe  of  the  lamp, 
and  constitutes  its  principal  defect.  This  defect  would  disap- 
pear in  the  most  natural  manner  if  the  glass  globe  were  sup- 
pressed, which  is  all  that  shows  the  trouble,  and  in  many 
cases  this  can  be  done. 

The  luminous  center,  instead  of  being  reduced  to  a  daz- 
zling point,  has  a  certain  volume  ;  the  light  possesses  a  fixity 


FIG.  92. — Lamp-soleil  suspended,  perspective  view. 

almost  absolute,  and  a  yellow  tinge  very  agreeable  to  the 
retina,  which  is,  on  the  contrary,  so  sensitive  to  the  violet 
rays ;  there  need,  then,  be  no  fear  for  the  eye,  even  when  in 
the  presence  of  the  most  intense  lights.  This  can  serve  as 
additional  proof  of  what  the  ophthalmologists  have  long  ago 
11 


144:  THE  INCANDESCENT  LIGHT. 

stated,  that  the  artificial  lights  which  we  are  discussing,  al- 
ways weaker  than  that  of  the  sun,  do  us  no  injury  by  their 
intensity,  but  only  by  their  particular  nature. 

The  working  of  the  sun-lamp  is  as  simple  as  possible. 
Generally  it  is  suspended,  and  the  two  carbons,  placed  verti- 
cally, descend  by  their  weight  alone  just  as  fast  as  they  are 
consumed.  A  flexible  wire  conducts  the  electrical  currents, 
and  follows  them  up  without  difficulty  in  their  movement  of 
descent  (Fig.  92).  When  one  wishes  to  incline  or  reverse  the 
position  of  the  lamp,  the  carbons  are  pushed  by  ordinary 
helical  springs,  or  else  by  counter- weights. 

The  carbons,  too,  are  of  very  ordinary  quality,  do  not  need 
much  purity,  and,  because  of  their  size,  bum  very  slowly- 
only  a  centimetre  an  hour  when  they  are  hard,  like  retort-car- 
bons, at  the  most  double  that  when  they  are  soft.  Thus  there 
is  no  trouble  in  putting  in  the  apparatus  carbons  long  enough 
to  burn  fifteen  or  sixteen  hours — that  is  to  say,  more  than  is 
ever  required  in  practice.  The  lamp,  all  prepared,  only  costs 
five  francs,  which  gives  some  idea  of  its  simplicity. 

As  in  the  candle  systems,  alternating  currents  are  used  for 
lighting,  so  that  the  two  rods  of  carbon  are  used  equally. 
The  rustling  inseparable  from  this  kind  of  current  is  quite 
disagreeable.  It  is  almost  entirely  suppressed  or  concealed 
now  by  placing  the  lamp  in  a  closed  lantern,  the  inconven- 
ience of  which  we  have  already  seen.  But  this  trouble  can 
be  avoided,  on  the  other  hand,  by  using  continuous  currents. 

From  the  point  of  view  of  its  electrical  working,  the  sun- 
lamp  can  be  subjected  to  great  variations  in  current  without 
the  fixity  and  coloration  of  its  light  being  sensibly  affected, 
and  it  resists  to  a  very  high  degree  the  causes  of  extinction. 
None  of  the  systems  of  regulator  lighting  can  be  compared 
to  it  in  these  respects  ;  as  it  is  also  superior  from  this  point  of 
view  to  open-air  incandescent  lamps,  of  which  we  have  spoken 
in  the  preceding  chapter. 

If,  in  consequence  of  a  variation  of  the  dynamo  speed 
caused  by  a  slipping  belt,  for  instance,  or  by  any  other  cause, 
the  intensity  of  the  current  diminishes,  the  luminous  intensity 
alone  will  diminish.  To  produce  extinction  of  the  light,  it 
will  be  necessary  for  the  current  to  fall  more  than  one  half, 
and  to  remain  at  this  degree  of  weakness  for  nearly  a  minute. 

A  sudden  increase  in  intensity  of  current  will  present  still 
less  inconvenience,  even  after  it  will  have  reached  such  a  degree 


THE  SUN-LAMP.  145 

as  would  constitute  a  serious  danger  for  many  other  systems. 
The  sun-lamp  endures,  for  instance,  without  the  least  trouble, 
a  current  three  or  four  times  stronger  than  the  normal  cur- 
rent, which  is  entirely  beyond  any  variations  which  can  be 
expected.  The  only  result  that  follows  is  the  sudden  raising 
to  a  value  of  five  hundred  carcels  the  lamp  which  formerly 
only  was  giving  the  quarter  of  it.  But  all  soon  returns  to 
regular  order,  without  any  part  of  the  apparatus  being  dis- 
organized. 

This  exceptional  power  of  resistance  to  electrical  varia- 
tions is  especially  due  to  the  action  of  the  incandescent  re- 
fractory substance,  which  stores  up  and  restores  heat  as  we 
have  explained  above. 

Nevertheless,  as  an  extinction  can  be  produced  all  the 
same,  it  is  provided  for  by  placing  two  lamps  in  the  same  cir- 
cuit. Only  one  should  work,  the  second  is  simply  designed 
to  replace  the  first  in  case  of  accident.  The  thing  is  done  in- 
stantaneously, without  need  of  any  personal  aid,  by  means  of 
an  automatic  switch,  which  turns  the  current  from  one  lamp 
into  the  other.  This  switch  is  governed  by  a  small  electro- 
magnet placed  in  a  derived  circuit.  If  the  working  lamp  goes 
out,  the  principal  current,  suddenly  stopped,  is  forced  into  the 
derived  circuit,  and  augments  enormously  the  force  of  the 
small  electro-magnet,  which  thus  becomes  capable  of  moving 
the  switch. 

It  would,  without  doubt,  be  simpler  to  relight  the  same 
lamp,  as  it  is  always  ready  in  spite  of  its  temporary  extinc- 
tion. For  this  the  points  of  the  carbons  must  be  brought  to- 
gether so  as  to  re-establish  the  voltaic  arc.  MM.  Clerc  and 
Bureau  have  combined  with  the  lamp  a  little  regulator,  with 
derived-current  solenoid,  which  produces  this  result  automat- 
ically. But,  simple  as  this  arrangement  is,  it  complicates 
the  apparatus  a  little,  and  takes  away  from  it  in  part  its  char- 
acter of  perfect  simplicity  which  makes  it  so  remarkably  free 
from  derangement. 

IV. 

According  to  experiments  made  in  Brussels,  in  the  month 
of  September,  1880,  by  M.  Desguin,  for  the  International  Con- 
gress of  Commerce  and  of  Industry,  the  sun-lamp  needs  no 
more  motive  power  than  the  best  regulator  systems,  and  its 
carbons  cost  much  less.  But,  before  pronouncing  upon  these 


THE   SUN-LAMP. 

different  points  finally,  it  is  necessary  to  wait  for  prolonged 
practical  experiments  on  a  large  scale. 

These  experiments  the  sun-lamp  is  still  too  recent  to  have 
furnished,  although  it  has  already  been  produced  in  public 
in  Brussels,  its  native  country,  in  London,  and  in  Paris.  In 
Brussels  it  has  lighted  for  a  long  time  one  of  the  large  coffee- 
houses of  the  city. 

At  Paris  it  has  been  in  use  for  a  month  in  the  entrance  to 
the  passage  Jouffroy  (Fig.  93)  and  in  the  mayoralty -house  in 
the  Rue  Drouot,  where  it  produced  a  very  good  impression ; 
it  participated  brilliantly  in  the  national  fete  of  July  14th, 
1881,  in  the  Place  de  Chateau  d'Eau.  Soon  it  will  be  seen 
under  more  difficult  conditions. 

M.  Ch.  Gamier  proposes,  in  fact,  to  choose  it  for  trying, 
at  the  same  time  with  the  Edison  light,  the  electric  lighting 
of  the  grand  lobby  of  the  Opera,  where  the  gas  is  in  a  fair 
way  to  destroy  the  beautiful  pictures  of  Baudry.  The  Edi- 
son light  is  to  fill  all  the  lusters,  and  the  sun-lamp,  hidden  in 
the  ornaments  of  bronze,  will  cast  upon  the  platform  floods  of 
light  whose  origin  can  not  be  seen  by  the  spectators.  This 
new  light,  which  produces  hardly  any  heat,  will  permit  soon 
a  useful  effectual  cleaning  of  the  works  of  Baudry,  so  badly 
blackened  by  the  pestiferous  exhalations  of  gas. 

At  London  twenty -four  sun-lamps  have  been  established 
since  the  month  of  July,  1881,  in  the  Westminster  panorama, 
where  it  appears  that  they  have  won  the  suffrages  of  all.  No 
one,  in  fact,  can  deny  that  they  are  not  far  superior  to  the 
regulator  lamps  for  the  lighting  up  of  pictures.  All  could  see 
this  at  the  Electrical  Exposition  at  Paris,  where  they  occupied 
a  room  entirely  furnished  with  cloths  of  all  kinds,  which  were 
not  all  very  bright  in  tone  nor  easy  to  be  lighted  up.  It  is 
certain  that  the  colors  underwent  no  alteration,  and  perhaps, 
indeed,  the  electric  light  made  the  designs  come  out  better 
than  does  the  daylight. 

The  effect  is  more  complete  still  when  the  lamps  are 
screened  by  a  cloth  on  the  side  of  the  observer,  as  the  picture- 
merchants  always  do  who  wish  to  display  their  merchandise. 
It  is  thus,  for  instance,  that  they  are  arranged  in  London  at 
the  Westminster  panorama,  and  the  arrangement  adopted  in 
Paris,  in  the  grand  lobby  of  the  Opera,  is  equivalent  to  this, 
as  the  luminous  centers  are  not  visible. 


14:8  THE  INCANDESCENT  LIGHT. 

CHAPTER  IV. 

THE    EDISON    LAMP. 

AMERICAN  as  he  is,  Edison  has  no  need  of  introduction  to 
the  European  public.  His  name  has  already  won  everywhere 
the  celebrity  of  great  inventors  by  a  crowd  of  discoveries, 
mostly  relating  to  electricity  ;  it  is  enough  to  cite  the  phono- 
graph and  carbon-telephone,  which  has  almost  everywhere 
replaced  the  telephone  of  Graham  Bell. 

It  was  in  1878  that  Edison  began  to  be  occupied  with  the 
electric  light.  His  project  was  conceived  during  a  voyage  to 
the  Rocky  Mountains,  in  company  with  Draper,  whose  many 
scientific  works,  translated  into  all  the  languages  of  the  Old 
World,  have  made  his  name  as  popular  in  Europe  as  in 
America.  On  his  return  he  set  to  work  immediately,  with  the 
promptitude  of  resolution  which  characterizes  his  compatriots. 

His  laboratory,  in  Menlo  Park,  was  already  full  of  tele- 
phones or  of  phonographs  of  all  kinds,  and  of  materials  and 
apparatus  designed  to  perfect  them.  In  the  twinkling  of  an 
eye  all  these  were  sent  to  the  storehouse,  to  give  place  to  a 
new  order  of  work,  corresponding  to  a  different  character  of 
studies,  even  if  electricity  was  still  the  base  of  work. 

I.   His  FIRST  RESEARCHES. 

In  this  territory,  already  well  worked  over  during  several 
years,  Edison  "took  the  bull  by  the  horns"  by  placing  before 
himself  the  problem  in  its  full  extent  and  under  the  most 
extreme  difficulties.  He  sought  for  a  complete  solution  ;  to 
make  it  do  everything  which  gas  could  do— in  furnishing 
a  light  of  constant  intensity,  easily  manageable,  capable  of 
being  placed  everywhere  in  small  amounts  like  our  actual 
gas-jets,  corresponding  to  eight  or  sixteen  candles — that  is,  to 
one  or  to  two  carcels  ;  but  he  was  to  make  it  do  all  this  better 
than  gas,  in  giving  a  light  deprived  of  all  odor,  which  would 
not  transform  salons  into  furnaces,  and  would  emit  no  vapor 
injurious  to  the  health  of  man,  destructive  to  furniture  or 
to  delicate  pictures,  multiplied  around  us.  This  is  the  prob- 
lem corresponding  at  once  to  the  fixity  and  divisibility  of  the 
electric  light.  It  remains  to  see  to  what  extent  and  at  what 
price  this  programme  has  been  carried  out. 


THB 

UWVE-RSIT7 


Fio.  94. 


150  THE  INCANDESCENT  LIGHT. 

Edison  naturally  began  with  the  voltaic  arc  *  used  now  in 
most  of  the  known  systems.  This  voltaic  arc,  whose  lumi- 
nous working  has  been  explained  in  a  preceding  chapter,  did 
not  give  a  steady  light,  which  is  principally  due  to  two  causes  : 

First,  the  electric  current  which  flows  from  one  carbon-pole 
to  the  other  is  less  a  true  current  than  a  very  rapid  succes- 
sion of  instantaneous  currents  or  sparks ;  this  electrical  dis- 
continuity creates  a  sort  of  luminous  flickering  very  painful 
to  the  eye,  and  accompanied  besides  very  often  by  a  sonorous 
hissing.  Finally,  the  carbon-poles,  which  appear  to  us  very 
thin,  are  in  reality  very  large  compared  to  the  electrical  mole- 
cules ;  now,  the  current  passes  from  one  pole  to  the  other, 
following  the  line  of  the  warmest  particles  of  air,  because  the 
heating  renders  them  better  conductors,  and  this  line  can  not 
always  be  the  same  in  air  disturbed  by  currents.  Then  each 
electric  discharge  from  a  pole  starts  from  the  part  of  the  pole 
where  the  tension  is  greatest,  and  this  point  also  will  vary. 

On  account  of  these  and  still  other  circumstances,  the  vol- 
taic arc  which  oscillates  from  right  to  left  and  left  to  right,  at 
the  same  time  oscillates  also  in  a  certain  sense  from  above 
downward  and  the  reverse,  because  it  is  formed  by  distinct 
successive  discharges.  Here  was  a  double  obstacle  to  over- 
come to  obtain  a  light  of  constant  intensity  such  as  Edison 
wanted. 

Seeing  no  good  practical  means  of  attaining  this  end,  he 
at  once  abandoned  the  voltaic  arc  and  its  troubles,  and,  with- 
out further  delay,  turned  to  the  other  method  of  developing 
electric  light :  the  incandescence  "of  a  conductor  traversed  by  a 
strong  current,  whose  molecules,  finding  no  longer  a  sufficient 
free  passage,  rub  one  against  the  other,  come  in  contact  with 
the  material  molecules,  and  heat  this  insufficient  passage  up 
to  a  high  temperature. 

The  idea  was  not  new  in  itself,  for  it  went  back  at  least  a 
third  of  a  century — that  is  to  say,  to  1845 — as  we  have  seen  in 
a  preceding  chapter.  More  recently,  in  1873,  a  Russian  physi- 
cist, M.  Lodyguine,  took  up  the  idea  of  Starr,  and  had  been 
followed  in  his  turn  by  several  others.  Unfortunately,  he 
came  in  contact  with  a  decisive  obstacle,  from  the  industrial 

*  [Mr.  Edison  worked  from  the  first  on  an  incandescent  lamp.  Later  he  ex- 
perimented with  the  arc-light  with  a  view  to  rendering  it  steady,  and  for  this 
purpose  patented  a  lamp  in  which  one  or  both  of  the  carbon  electrodes  were 
given  a  rapid  rotary  motion.] 


THE   EDISON   LAMP.  151 

point  of  view,  though  it  may  seem  of  little  account  in  the  eyes 
of  the  savant :  this  obstacle  is  the  cost  of  production. 

Incandescence  is  not  subject  to  two  causes  of  trouble  that 
affect  the  voltaic  arc ;  it  can,  then,  if  it  avoids  the  perils  of 
another  sort,  furnish  a  perfectly  steady  light.  But  the  in- 
candescent body  presents  a  cooling  surface  much  larger,  and 
radiates  heat  more  easily,  than  the  particles  of  air  heated  by 
the  voltaic  arc.  It  loses,  then,  much  more  energy  without 
useful  result — that  is  to  say,  without  corresponding  light. 
In  other  terms,  the  economical  return  of  the  system  is  very 
small ;  with  the  same  source  of  electricity  the  incandescent 
system  furnishes  much  less  light  than  the  voltaic  arc  ;  in  con- 
sequence, this  light  costs  more.  Now,  a  light  that  is  too 
costly,  whatever  be  its  other  good  qualities,  is  in  practice  a 
Utopia. 

The  weak  point  of  the  system,  it  will  be  seen,  resides  in 
the  matter  that  is  made  incandescent.  If  the  defects  of  the 
substance  in  question  could  be  suppressed  or  at  least  restrained 
to  a  sufficient  extent,  the  rest  could  be  arranged..  It  is,  then, 
on  the  class  of  material,  and  the  disposition  to  be  made  of  it, 
that  all  his  care  was  to  be  expended,  as  this  was  the  root  of 
the  whole  matter.  Edison  was  not  wanting.  To  attain  his  end, 
he  was  obliged  to  display  marvels  of  tenacity  and  patience, 
and  use  at  the  same,  time  the  immense  means  of  action  which 
American  capitalists  gladly  place  at  the  service  of  inventors. 

This  incandescent  material  also,  like  the  valet  of  the  com- 
edy, should  unite  many  qualities  in  itself  which  are  very  diffi- 
cult to  find.  In  the  first  place,  it  should  remain  incandescent 
without  burning,  otherwise  the  apparatus  would  be  consumed 
immediately,  and  would  be  unable  to  afford  any  real  service. 
In  the  second  place,  it  should  offer  to  the  passage  of  the  cur- 
rent a  resistance  precisely  such  as  would  bring  about  the  in- 
crease of  heating  which  produces  incandescence.  In  the  third 
place,  it  should  be  infusible  under  the  influence  of  this  high 
degree  of  heat,  so  as  not  to  disappear  as  quickly  as  if  it 
burned.  In  the  fourth  place,  it  should  also  not  be  oxidizable, 
which  would  bring  about  its  destruction  the  same  as  if  by  an 
ordinary  combustion. 

In  the  fifth  place,  as  it  should,  for  increasing  the  resistance 
to  the  current,  be  reducible  to  fine  filaments  like  a  woman's 
hair,  it  should  be  capable  of  preserving  a  rigid  form  even  at 
this  state  of  ideal  thinness.  In  the  sixth  place,  it  should  be 


152 


THE   INCANDESCENT  LIGHT. 


arranged  to  diminish  as  much  as  possible  the  conductivity  of 
its  middle  section,  for  electricity,  and,  above  all,  for  heat,  so 
as  to  avoid  the  chilling  which  would  carry  with  it  a  consider- 
able loss  of  energy — a  loss  which  constitutes  the  principal 
trouble  of  the  system.  In  the  seventh  place — but  the  enu- 
meration is  not  nearly  ended,  and  enough  is  presented  here 
to  illustrate  the  difficulties  of  the  subject.  What  substance 
would  be  worthy  of  being  the  valet  of  so  exacting  a  master  ? 


II.   PLATINUM- WIRE  LAMPS. 

Edison  first  tried  platinum  and  the  very  rare  metals  which 
are  called  metals  of  the  platinum  group,  as  they  are  usually 
found  associated  with  it  in  the  same  minerals.  Platinum 

is  easily  reduced  to  as 
thin  wire  as  can  be  de- 
sired, even  to  the  point 
of  being  invisible ;  even 
in  this  state  of  fineness  it 
retains  enough  consist- 
ence to  keep  the  shape 
that  is  given  to  it,  and 
its  flexibility  suffers  it 
to  be  rolled  in  all  con- 
ceivable directions  with- 
out breaking.  Edison 
made  with  it  a  small 
spiral,  which  he  inclosed 
in  a  vessel  of  glass  as 

FIG.  95.— Sketch  of  Edison's  first  lamp.     From  his         , 

French  patent.  LBTge  as  a  small  apple. 

This  vessel,  which  real- 
ly had  the  shape  of  an  apple,  was  closed  at  its  base  by  a  mass 
of  plaster  which  the  metallic  conductors  passed  through,  con- 
ducting the  current  through  the  platinum  spiral  destined  to 
illuminate  by  incandescence  (Fig.  95). 

Here  was  the  Edison  lamp,  in  its  first  design,  perfectly  in- 
dependent in  its  movements,  and  capable  of  assuming  all  forms 
and  all  shapes  that  could  be  desired.  It  sufficed,  in  fact,  to 
make  the  apparatus  work,  to  place  the  metallic  conductors  in 
contact  with  any  wires  bringing  the  electric  current,  perhaps, 
from  a  great  distance,  and  these  electrical  wires  would  be  sus- 
ceptible of  gliding  into  all  corners,  like  the  wires  of  electric 


THE  EDISON  LAMP. 


153 


FIG.  96.— Edison  lamp  with  incandescent  platinum  spiral,  pro- 
vided with  safety  apparatus.    (French  patent,  1879). 


a,  spiral  of  platinum,  to 

be  rendered  incan- 
descent. It  is  at- 
tached to  two  bind- 
ing-posts. That  on 
the  right  is  connect- 
ed by  the  wire  m 
with  the  top  plate  d ; 
the  other  is  attached 
by  a  wire  x  to  the 
piece  *,  and  the 
outgoing  wire  n. 

b,  glass  cylinder  con- 
taining the  spiral  a, 
in  which  a  vacuum 
can    be    produced. 
Mr.     Edison    indi- 
cates also  the  em- 
ployment  of  two 
concentriccylinders, 
the    annular    space 
between  which  may 
contain  certain  liq- 
uids,   such    as    the 
sulphate  of  quinine. 

d,  top  plate  of  cylin- 
der*. 

x  x',  small  metallic  rod 
passing  through  the 
center  of  the  spiral 
a,  and  descending  so 
as  to  rest  upon  the 
lever  «,  which  it 
forces  down  when- 
ever it  is  elongated 
by  the  expansion 
due  to  the  heat  de- 
veloped in  it  by  the 
passage  of  the  cur- 
rent, and  by  the  ra- 
diation from  the  in- 
candescent spiral. 
s,  lever  pivoted  at  o,  and 
insulated.  When  it 


is  pressed  down  by  the  rod  x  x',  it  forms  a  contact  at  its  extremity  with  the  piece  *',  and 
provides  a  passage  for  a  part  of  the  current  flowing  through  the  spiral. 

«,  piece  carrying  the  safety  contact  and  its  regulating  screw  r. 

P,  N,  p,  n,  A,  &,  wires  and  binding-posts  for  the  entrance  and  departure  of  the  current. 

y,  base  of  the  cylinder  b. 

e,f,  g,  foot  of  the  lamp. 

The  current  arrives  at  P,  passes  through  P,  N,  S,  x  x',  ^,  m,  c,  a,  c',  i,  n,  &,  N.  The 
shunt  is  established  through  S,  t,  n.  It  is  evident  that  this  arrangement  causes  an  inter- 
mittent action,  which  renders  it  very  difficult  to  obtain  uniformity  of  light  in  the  spiral  a. 

bells  now  universally  used.  Nothing  can  be  imagined  more 
simple  in  its  general  aspect ;  we  shall  see  that  this  apparent 
simplicity  hid  many  real  complications  (Fig.  96). 


154: 


THE  INCANDESCENT  LIGHT. 


[Another  form  of  this  lamp,  and  the  one  which  Mr.  Edison 
designed  using  before  he  succeeded  with  carbon,  is  shown  in 
Fig.  97.  The  platinum  wire  is  coiled  upon  a  spool  of  lime  or 
similar  infusible  material,  d,  which  is  supported  by  a  stick,  e, 
of  the  same  material.  The  terminal  wires,  /,  </,  of  the  coil 
are  sealed  into  the  glass  of  the  inclosing  envelope,  B,  in  which 

a  vacuum  is  produced.  The  glass,  B, 
is  placed  within  another,  c,  which  is 
closed  by  a  base-piece  containing  an 
aneroid  chamber,  n,  operated  by  the 
expansion  of  the  air  between  the  two 
glasses.  When,  on  account  of  too  much 
current  passing  through  the  platinum 
spiral,  this  air  is  abnormally  heated, 
the  lower  surface  of  the  chamber,  n, 
becomes  distended,  and,  through  the 
medium  of  the  post,  o,  depresses  the 
lever,  p,  and  breaks  the  circuit  at  R. 
This  remains  interrupted  until  the  con- 
traction of  the  air  allows  the  lever  to 
move  upward  and  again  make  contact. 
A  regulating  screw  serves  to  adjust  the 
frame  carrying  the  lever,  and  hence  the 
expansion  neces- 
sary to  break  the 
circuit.  ] 

In  the  small 
glass     globe, 

where  the  light  spiral  of  platinum  was 
horizontally  extended,  a  vacuum  had 
to  be  maintained  for  several  reasons : 
first,  to  diminish  the  loss  of  electric- 
ity, and,  above  all,  of  heat ;  finally,  to 
prevent  the  oxidation  of  the  platinum, 
facilitated  by  its  high  temperature. 

When  a  vacuum  was  produced  by  some  of  the  highly  per- 
fected processes,  which  we  shall  presently  describe,  the  differ- 
ent gases  retained  in  the  pores  of  the  platinum  escaped. 
Thereupon,  under  the  action  of  the  passage  of  the  current, 
the  metal  presented  entirely  new  physical  properties,  so  that 
some  physicists  supposed  it  to  be  a  new  metal.  It  became 
hard  like  steel,  became  as  susceptible  of  polish  as  silver,  and 


FIG.  97.— Edison's  platinum 
lamp,  with  regulator  oper- 
ated by  expansion  of  heat- 
ed air. 


THE  EDISON  LAMP.  155 

acquired  a  very  high  degree  of  elasticity,  which  facilitated 
greatly  the  fantastic  twistings  to  which  it  was  subjected.  But, 
above  all,  it  acquired  a  much  greater  calorific  capacity,  and 
only  fused  at  a  very  high  temperature,  so  that  it  could  be 
made  much  more  luminous.  Edison  even  states  that  he  suc- 
ceeded in  thus  obtaining  a  light  equal  to  eight  candles  with  a 
wire  that  under  ordinary  circumstances  could  only  have  given 
a  light  of  one  candle. 

The  spiral  shape  given  to  the  platinum  wire  was  designed 
to  diminish  the  loss  of  heat  due  to  radiation.  Every  turn  of 
the  spiral  or  helix  radiated  heat  upon  the  other  spirals,  so  that 
a  part  of  the  heat  radiated  is  utilized  in  a  mutual  reheating 
of  the  spirals  one  by  the  otljer.  To  further  diminish  the  loss 
of  heat  the  wire  was  covered,  by  means  of  a  brush,  with  a  thin 
coating  of  a  metallic  oxide ;  a  number  of  oxides  were  tried, 
those  of  the  alkaline  earth  metals,  and  a  great  number  of  others 
from  magnesia,  lime,  and  zinc  oxide,  up  to  the  oxides  of  the 
rarer  metals,  of  glycenium,  zirconium,  and  even  of  thorium. 

In  spite  of  all  his  efforts,  Edison  was  forced,  like  many 
others  before  him,  to  abandon  platinum  and  its  related  metals. 
The  wires  melt  when  the  current  acquires  too  high  an  inten- 
sity, or,  if  it  does  not  melt,  it  disintegrates,  and  is  thus  rap- 
idly rendered  useless. 

III.  LAMPS  WITH  PAPER  CARBON. 

Having  abandoned  platinum,  Edison  turned  his  attention 
fco  carbon,  which  assumes  in  nature  so  many  different  forms. 
Already,  in  1877,  before  studying  the  electric  light,  while  still 
working  on  the  telephone,  he  had  several  times  made  obser- 
vations which  would  lead  him  in  this  direction.  It  was  in 
repeating,  with  slight  variation,  the  experiment  known  under 
the  name  of  the  electric  cascade.  A  sphere  of  glass  filled  with 
mercury  is  so  arranged  as  to  empty  itself  through  a  little  hole 
at  the  same  time  that  a  current  of  electricity  traverses  the 
mercurial  cascade,  which  it  fills  with  marvelous  effects  of 
light.  Edison  conceived  the  idea  of  placing  in  the  glass 
sphere  a  rod  of  carbon  for  the  current  to  pass  through.  This 
rod  became  incandescent  without  burning,  because  it  was  not 
surrounded  by  air,  but  with  mercury,  or  at  least  a  mercurial 
atmosphere.  The  incandescence  appeared  much  more  vivid 
than  in  air. 


156  THE   INCANDESCENT   LIGHT. 

It  was  also  under  analogous  conditions  that  the  first  ex- 
perimenters with  the  electric  light  by  incandescence,  in  1845, 
had  worked  :  we  refer  to  King  and  Starr.  But  they  produced 
their  vacuums  by  means  of  a  common  air-pump,  which  re- 
moved the  air  very  imperfectly,  so  that  the  vacuum  left  by  a 
removal  of  mercury  (barometric  or  Torricellian  vacuum,  as  it 
is  usually  called)  is  far  more  complete.* 

Edison  would  then  have  at  once  experimented  with  carbon 
if  he  had  not  been  stopped  by  the  difficulty  of  obtaining  fila- 
ments of  carbon  as  fine  as  those  of  platinum,  flexible  enough 
to  permit  of  bending  without  breaking,  and  at  the  same  time 
firm  enough  to  keep  the  form  which  might  be  given  them.f 
Nevertheless,  one  day,  when  lighting  his  cigar  with  a  rolled 
paper-lighter,  he  noticed  that  this  allumette,  once  extin- 
guished and  freed  of  its  ashes,  left  in  his  hand  a  thin  spiral, 
fragile  without  doubt,  but  which  lasted  for  some  time.  This 
spiral,  in  brief,  was  composed  of  vegetable  carbon.  A  means 
had  now  to  be  found  to  consolidate  it,  for,  as  it  was,  it  could 
not  carry  the  smallest  current,  and,  above  all,  it  was  necessary, 
according  to  the  method  of  complete  enumeration,  to  examine 
the  properties  and  applicability  of  all  the  forms  of  carbon  in 
nature. 

The  work  began  with  a  mixture  of  graphite  and  pitch, 
made  in  the  form  of  a  pencil,  and  carbonized  with  exclusion 
of  air  in  a  pistol-barrel.  But  this  did  not  work  well.  Edison 
returned  again  to  paper.  He  experimented  successively  with 
all  kinds  of  paper  used  in  all  countries,  even  with  special 
papers  which  he  had  made  expressly  for  himself;  for  ex- 
ample, with  one  made  from  a  silky  cotton,  very  high-priced, 
which  he  gathered  in  certain  islands  near  Charleston. 

[One  of  the  earliest  forms  of  the  carbon  lamp  was  that 
shown  in  Fig.  99,  in  which  the  carbon  filament  was  given  a 
spiral  form,  aud  joined  to  the  leading  wires  by  means  of  plas- 
tic carbon.] 

*  [Starr  used  a  Torricellian  vacuum,  but  this  was  far  from  being  perfect  enough 
to  prevent  the  waste  of  the  carbon.] 

t  [Mr.  Edison's  first  experiments  with  carbon  were  made  with  the  imperfect 
vacuum  of  a  mechanical  air-pump.  He,  therefore,  did  not  think  that  carbon 
could  be  made  to  stand ;  but,  after  finding  platinum  unsatisfactory,  he  returned 
to  carbon,  using  the  vacuum  obtainable  with  the  mercury  air-pump.  He  ex- 
perienced no  difficulty  in  obtaining  carbon  in  a  flexible  condition,  as  one  of  the 
earliest  forms  used  was  that  obtained  by  carbonizing  a  cotton  thread.] 


THE  EDISON   LAMP. 


157 


This  last  paper  gave  a  carbon  almost  absolutely  free  from 
ash — that  is  to  say,  of  a  homogeneity  which  seemed  almost 
perfect — an  indispensable  condition  for  the  regular  flow  of 
the  current,  and  consequent- 
ly for  the  steadiness  of  the 
light.    Nevertheless,  the  cur- 
rent did  not  circulate  with 
sufficient    regularity  in   the 
filament  of  carbonized  paper, 
and  the  cause  of  this  was 
next  determined. 

In  brief,  paper  consists  of 
cotton  fibers,  pressed  in  dis- 
order, one  on  top  of  the  oth- 
er, so  as  to  form  a  sort  of 
felting.  In  this  felting  the 
current  finds  no  continuous 
fibers  which  it  can  follow ; 
it  finds  fibers  placed  across 
its  track,  and  has  to  jump 
from  fiber  to  fiber,  like  a 
man  crossing  a  brook  on 
stepping-stones. 

Now,  each  of  these  leaps 
constitutes  a  very  small  vol- 
taic arc,  which,  quite  invisi- 
ble to  our  eyes,  none  the 
less  changes  the  nature  of 
the  current,  which  ceases  to 
be  a  continuous  one.  More- 
over, these  small  interior 
sparks  destroy  the  paper. 

The  discovery  was  impor- 
tant :  it  led  him  to  discard 
all  artificial  products — for, 
necessarily,  it  would  pre- 
sent this  irregular  felting, 
the  cause  of  all  the  trouble 


FIG.  98.— Edison  lamp  with  Bristol-board  car- 
bon, according  to  his  French  patent  of  May 
28,  1879. 

This  lamp  consists  of  a  glass  globe  A, 
in  which  a  vacuum  is  created. 

This  globe  is  supported  by  a  wooden 
foot  B,  provided  with  binding-screws  D, 
D,  to  receive  the  electric  wires  which  pass 
into  the  interior  of  the  globe  through  a  con- 
ical piece  of  insulating  material  E  E,  and 
terminates  in  two  platinum  plates  G,  G, 
twisted  into  figure  eight  forms. 

The  extremities  of  these  platinum  plates 
are  fastened  to  the  two  ends  of  the  carbon 
horseshoe. 


—only    natural    fibers,   pro- 
duced by  an  exceedingly  slow  work  of  natural  growth,  could 
present  the  perfect  homogeneity  necessary  for  the  regular 
passage  of  the  current.     Decidedly,  the  works  of  nature  were 


158 


THE  INCANDESCENT  LIGHT. 


still  good  for  something  ;  even  an  American,  and  certainly 
no  ordinary  one.   had    to  recognize  the   fact  that   human 

mechanism    could    not  do 

everything. 

IV.   BAMBOO-CAKBON 
LAMPS. 

He  then  set  to  work  to 
collect  all  the  woods  or 
natural  fibers  of  all  coun- 
tries that  seemed  available. 
Special  agents  were  sent 
to  China  and  Japan.  A 
botanist  named  Segrador, 
went  through  the  south 
of  the  United  States,  then 
went  to  Havana,  where  he 
died,  of  yellow  fever,  when 
on  the  point  of  embark- 
ing, after  having  a  short 
time  before  escaped  mercu- 
rial poisoning  in  the  Menlo 
Park  laboratory.  A  fourth, 
named  Brennan,  who  had 
already  accompanied  Louis 
Agassiz,  some  years  before, 
in  his  great  scientific  voy- 
age to  Brazil,  went  there 
again  to  collect  plants  of 
all  kinds,  and  he  fortunate- 
ly fared  very  well. 

Soon  a  great  variety  of 
woods  and  plants  began  to 
accumulate  in  Menlo  Park. 
Only  three  plants  withstood 
the  tests,  and  of  these  bam- 

$  boo  was  chosen  as  the  most 

perfect.  But  there  are  many 
varieties  of  bamboo  to  be 
chosen  from,  and  nothing 

Fia.  99.— Edison's  carbon  lamp  with  spiral  fila-  IIP  A 

ment.    (American  patent,  Jan.  27,  1880.)  must  be   left  to  chance.       A 


THE  EDISON  LAMP. 


159 


reliable  agent,  Mr.  Moore,  was  sent  to  China  to  visit  all  the 
workshops  where  bamboo  products  were  produced — all  the 
plantations,  all  the  localities  where  the  plant  may  have  suf- 
fered a  modification  ;  he  even  thought  of  trying  old  pieces  of 
bamboo  that  came  from  structures  several  hundred  years  old. 
The  variety  which  proved  superior  to  all  the  others  was  a 
species  of  Japanese  bamboo,  which,  moreover,  was  found  in 
considerable  quantity,  so  that  there  was  no  danger  of  its  sup- 
ply running  short,  even  when  the  new  lamps  would  have 
everywhere  replaced  the  old  methods  of  illumination. 

The  qualities  which  had  most  to  do  in  determining  this 
choice  were  the  regularity  of  the  fibers,  and,  above  all,  the 
facility  of  division.     The  threads,  in  short,  should  only  be  one 
fifth  of  a  millimetre  in  thickness.     At  first  they 
were  made  round ;  now  they  are  flattened,  and 
still  thinner,  for  their  thickness  does  not  exceed 
two  tenths  of  a  millimetre,  and  their  width  three 
and  a  half  tenths  (Fig.  100). 

This  work  of  dividing  the  filaments  is  now 
done  mechanically,  with  perfect  regularity,  mar- 
velous promptitude,  and  remarkable  economy, 
qualities  most  of  all  to  be  valued  in  a  good  man- 
ufacturing process. 

Instead  of  the  spiral  form  of  the  former  plat- 
inum wires,  to-day  the  carbon  threads  have  the 
shape  of  a  more  or  less  prolonged  horseshoe, 
because  the  bamboo  carbon  does  not  submit  to 
as  tortuous  shapes  as  platinum  wire  can  assume. 

Finally,  the  most  troublesome  part  of  the 
fabrication  of  lamps  is  the  extraction  of  the  air, 
by  a  mercury-pump.  Existing  forms  of  pumps  were  first 
employed,  such  as  Sprengel's  and  Geisler's.  But  the  mer- 
cury had  to  be  poured  by  hand,  a  difficult  and  dangerous 
operation,  which  almost  poisoned  Edison  and  his  principal 
collaborators,  notably  Messrs.  Batchelor  and  Moses,  who 
afterward  represented  him  in  Paris,  and  poor  Segrador,  who 
died  from  another  cause,  in  Havana. 

[The  Geisler  pump  consists  of  a  glass  bulb  of  considerable 
size  on  the  upper  end  of  a  vertical  glass  tube  of  large  bore 
(from  three  to  five  eighths  inch  in  diameter).  To  the  lower  end 
of  this  tube  a  reservoir  of  mercury  (usually  a  glass  bulb  holding 
from  thirty  to  forty  pounds)  is  connected  by  a  flexible  rubber 

12 


FIG.  100.— Lamp 
with  horse-shoe 
filament. 


160 


THE   INCANDESCENT  LIGHT. 


tube.  The  former  bulb  is  placed  so  as  to  be  more  than  thirty 
inches  above  the  level  of  the  mercury  in  the  reservoir.  By 
raising  this  latter  the  upper  bulb  can  be  filled  with  mercury, 


Eight-candle  lamp  with  single  filament. 


Lamp  with  double  filament  in  the  form  of 
a  cross,  of  sixteen  candles. 


Thirty-two-candle  lamp  with  four  parallel 
filaments. 


Sixteen-candle  lamp  with  double  parallel 
filaments. 


FIGS.  101,  102, 103,  104.— The  actual  Edison  lamps. 


THE  EDISON  LAMP. 


161 


and  its  air  displaced.  Leading  from  the  top  of  this  bulb  is  a 
tube  to  which  the  lamps  to  be  exhausted  are  attached.  By 
means  of  a  two-way  cock,  communication  with  the  lamps  can 
be  shut  off  while  the  air  is  being  driven  out  of  the  bulb,  and 
opened  when  the  mercury  recedes  into  the  reservoir.  To  ob- 
tain a  high  vacuum  with  this  pump  the  mercury  has  to  be 
lifted  a  great  number  of  times,  so  that  its  operation  by  hand 


FIG.  105.— Edison  lamp  provided  with 
regulator  of  intensity. 


FIG.  106.— Carbon-rod  rheostat  of  the 
regulator  of  intensity. 


is  very  tiresome.  When  it  is  used  in  the  manufacture  of  in- 
candescent lamps  it  is  operated  by  power.  The  neck  of  the 
reservoir  is  usually  closed  by  a  tuft  of  cotton,  so  that  there 
are  no  mercurial  fumes  from  the  pump. 

The  Sprengel  pump,  in  its  simplest  form,  consists  of  a  fine- 
bore  barometer-tube,  through  which  a  stream  of  mercury  con- 
stantly falls  from  a  reservoir  placed  above.  This  tube  is 
somewhat  enlarged  at  its  upper  end,  from  which  extends  a 


162 


THE  INCANDESCENT  LIGHT. 


tube  leading  to  the  lamps  to  be  exhausted.  The  mercury  is 
discharged  into  the  barometer-tube  from  a  fine  spout  entering 
this  enlarged  portion.  This  falling  stream  draws  the  air  with 

it  and  discharges  it  below  into  a 
mercury-cup,  into  which  the  fall- 
tube,  as  it  is  called,  dips.  The 
action  of  this  pump  is  very  slow, 
but  the  best  vacuum  can  be  ob- 
tained with  it.  The  mercury  has 
to  be  from  time  to  time  removed 
from  the  lower  receptacle  and 
poured  back  into  the  reservoir, 
an  operation  that  subjects  the 
attendant  to  hurtful  mercurial 
fumes.  When  this  pump  is  used 
in  manufacturing,  the  mercury  is 
raised  by  power,  the  operation 
being  a  continuous  one.  It  is 
then  free  from  vapors,  as  the 
mercury  moves  in  a  closed  chan- 
nel. A  combination  of  these  two 
pumps  is  frequently  employed.] 

To-day  the  pumps,  like  the 
rest  of  the  apparatus,  are  sim- 
plified, but  after  a  hundred  dif- 
ferent trials.  There  are  now  five 
hundred  at  Menlo  Park,  which 
work  automatically,  without  mer- 
curial emanations,  without  dan- 
gerous or  disagreeable  manipu- 
lation, without  revealing  their 
presence  otherwise  than  by  a  pe- 
culiar noise  resembling  a  perpet- 
ual hail-storm.  The  perfection 
of  the  vacuum  is,  too,  one  of  the 
principal  qualities  of  the  appa- 
ratus, for  a  thread  of  carbon 
which  would  give  an  intensity 
of  ten  candles  in  the  vacuum  of 
an  ordinary  air-pump  would  give 

.  lor.-sixteen-candic  lamp  (three-     sixteen  candles  in  the  vacuum  of 
quarter  size).  a  mercury-pump. 


JFio.  108.— Crystal  chandelier  of  Edison  lamps,  used  at  the  Paris  Exposition  of 

Electricity. 


164 


THE  INCANDESCENT   LIGHT. 


V.  THE  LAMPS  ACTUALLY  EMPLOYED. 

The  exterior  form  of  the  lamp  has  been  several  times 
changed,  on  account  of  the  several  changes  in  shape  of  the 
incandescent  filament.  To-day  it  resembles  a  moderate-sized 
pear,  about  the  size  of  the  fist  of  a  child  of  six  or  eight  years 
old  (Figs.  101, 102,  103,  and  104).  They  are,  moreover,  of  two 
dimensions.  These  differ  not  only  in  their  exterior  size,  but 
also  in  the  length  of  the  carbon  horsehoe-thread,  which  is 
almost  twelve  centimetres  long  in  the  larger — those  called 

whole  lamps — and  is 
only  about  half  as  long 
in  the  half  lamps. 

The  luminous  intensi- 
ty naturally  varies  with 
the  intensity  of  the  elec- 
tric current  which  pass- 
es through  the  lamps. 
In  good  condition  it 
reaches  sixteen  candles 
—that  is  to  say,  about 
two  carcels  for  the  larg- 
er lamps,  and  half  that 
for  the  smaller  lamps. 
Nothing  prevents  their 
being  made  as  feeble 
as  wanted  ;  all  that  is 
necessary  is  to  shorten 
the  horseshoe,  which 
amounts  to  diminish- 
ing the  extent  of  the 

incandescent  luminous  surface.     If  necessary,  the  lamp  can 
thus  be  reduced  to  the  proportions  of  a  taper. 

Its  power,  on  the  other  hand,  can  be  increased,  by  the  in- 
troduction of  several  parallel  or  crossed  filaments  of  carbon 
(Fig.  103)  instead  of  a  single  one,  thus  creating  lights  capable, 
perhaps,  of  rivaling  the  voltaic  arc. 

Not  only  can  lamps  of  very  varying  intensity  be  thus  made, 
but  also,  by  means  of  a  particular  construction,  the  intensity 
of  any  given  lamp  can  be  made  to  vary  at  will  through  a  con- 
siderable range.  Edison  effects  this  by  placing  under  the  lamp 
a  regulator  of  intensity. 


FIG.  109.— Edison  lamp  with  shade. 


THE   EDISON  LAMP.  165 

It  is  a  cylindrical  rheostat,  containing  five  rods  of  carbon 
(Figs.  105  and  106),  which  can  at  will  be  interposed  in  the 
lamp  circuit  by  rotating  the  foot  which  supports  them. 
These  carbon-rods,  of  varying  size,  produce  a  resistance  which 
diminishes  more  or  less  the  intensity  of  the  current  passing 
through  the  lamp.  The  result  thus  obtained  can  be  compared 
with  that  produced  in  an  oil-lamp  by  turning  the  wick  up  or 
down. 

The  lamp,  successively  improved  in  all  its  parts,  is  to-day 
more  substantial  than  would  have  been  deemed  possible. 
Some  are  in  existence  that  have  furnished  light  for  seven 
or  eight  hundred  hours  or  more.  For  the  rest,  the  loss  of  a 
lamp  is  an  accident  of  little  more  moment  than  the  break- 
age of  the  chimney  of  an  oil-lamp,  for  the  Edison 
lamp  costs  only  twice  the  price  of  the  fragile  glasses 
which  to-day  break  so  often  in  our  houses.  They 
are  sold  in  New  York  for  thirty-five  cents  *  (or  one 
franc  seventy -five  centimes),  and  it  seems  that  they 
can  be  produced  at  one  franc  twenty -five  centimes, 
on  account  of  economies  introduced  in  their  manu- 
facture. But  it  must  be  understood  that  this  price 
does  not  include  the  patentee' s  license,  which  must  be 
paid  in  addition,  if  the  light  be  privately  produced. 


FIG.  110.— Jointed  bracket  for  Edison  lamp.  The  joints  are  con- 
structed so  as  to  maintain  the  circuit  closed  in  all  possible 
positions  of  the  bracket. 

The  principal  accident  which  can  happen  to  the  incandes- 
cent lamp  during  manufacture  is  the  breakage  of  the  glass. 
After  having  blown  it  by  the  usual  processes,  it  is  reheated 
so  as  to  anneal  it,  which  makes  it  strong.  [The  work  of 
sealing  the  filament  into  the  globe  is  done  before  the  blow- 
pipe. The  pear-shaped  envelopes  are  made  in  quantity  at  a 
factory,  and  are  frequently  blown  in  a  mold.  The  glass- 

*  [The  Edison  lamps  are  furnished  to  consumers  without  charge.  To  pur- 
chasers of  either  the  lamps,  or  of  a  complete  isolated  plant,  they  are  sold  at  a 
dollar  each.] 


166  THE  INCANDESCENT  LIGHT. 

blower  takes  one  of  these  and  attaches  to  its  top  a  small 
glass  tube,  which  serves  to  connect  the  lamp  to  the  pump 
for  exhaustion.  The  glass  stem  forming  the  base  of  the 
lamp,  with  the  platinum  leading  wires  sealed  into  it,  and  the 
filament  mounted  upon  them,  is  then  introduced  into  the 
neck  of  the  globe  and  united  to  it  by  fusion.  With  German 
glass  it  is  usually  necessary  to  blacken  the  exterior  of  the 


FIG.  111.— Edison  three-light  chandelier. 

globe  after  sealing,  to  prevent  cracking  by  too  rapid  cooling. 
This  is  usually  not  necessary  with  American  glass,  that  com- 
monly used  in  this  country  for  this  work.  After  exhaustion 
the  lamp  is  removed  from  the  pump  by  fusing  the  glass  at- 
tachment-tube, leaving  the  small  nipple  shown  in  the  figures.] 
The  thread  of  carbon  also  becomes  hard,  on  account  of  being 
subjected  to  the  passage  of  the  current  during  the  exhaustion 


THE  EDISON  LAMP.  167 

of  the  air,  which  action  produces  on  it  the  same  effect  as  on 
platinum. 

Another  accident,  equally  to  be  feared,  is  the  rupture  of 
the  carbon-thread  at  its  points  of  attachment.  To  avoid  it  as 
far  as  possible,  particular  precautions  are  followed  in  the 
mode  of  attachment  of  the  thread. 

The  two  ends  of  the  horseshoe-filament  are  enlarged  a 
little,  and  are  held  in  little  platinum  pincers,  *  which  form  the 
ends  of  the  platinum  wires,  serving  as  part  of  the  circuit  of 
the  electric  current  passing  through  the  carbon  horseshoe. 
The  whole  is  united  by  a  plating  of  copper,  f 

The  platinum  wires  are  naturally  much  larger  than  the 
carbon-thread,  so  they  are  not  heated  to  redness.  But  they 
do  heat,  nevertheless,  and  consequently  expand  when  the 
lamp  is  working.  When  it  is  extinguished,  they  return  to 
their  natural  size,  growing  smaller  as  they  cool.  Now,  these 
platinum  wires  traverse  the  mass  of  plaster  which  closes  the 
lamp  at  its  bottom.  Their  successive  dilatations  and  contrac- 
tions are  liable  to  cause  the  formation,  around  them  and 
through  this  mass,  of  a  little  tubular  passage,  through  which 
the  atmospheric  air  will  finally  insinuate  itself  little  by  little 
into  the  interior  of  the  lamp,  and  destroy  the  vacuum.  Some 
special  process  of  sealing  has  to  be  devised  to  meet  this  danger.:): 

This,  then,  is  the  actual  Edison  lamp,  the  latest  form  of 
which  is  shown  in  Fig.  107.  It  ends  below  in  a  screw-thread, 
by  which  it  can  be  fastened  on  any  kind  of  a  foot,  chandelier, 
candelabrum,  bracket,  etc.,  and  it  is  enough  to  turn  a  key 
placed  in  the  candelabrum  to  start  it  into  action  or  to  stop  it. 
The  mano3uvre  resembles  exactly  that  of  the  operation  of  a 
gas-cock. 

*  [These  are  no  longer  used,  the  carbon  filament  being  attached  directly  to 
copper  wire,  flattened  and  bent  so  as  to  form  a  sort  of  clamp.] 

t  [To  render  this  joint  an  enduring  one,  the  surface  of  contact  between  the 
carbon  and  the  platinum  must  be  cool.  This  is  effected  by  increasing  the  amount 
of  carbon  at  this  point,  either  by  enlarging  the  ends  of  the  filament,  moulding 
about  it  a  plastic  carbon,  or  forming  a  carbon  deposit  from  a  carbonaceous  gas 
or  liquid.] 

I  [In  the  Edison,  as  in  all  the  other  modern  incandescent  lamps,  the  leading 
wires  are  sealed  into  the  glass  envelope  by  fusion  of  the  glass  around  the  wires. 
No  other  mode  of  sealing  has  been  found  to  answer,  as  the  in-leakage  of  a  very 
small  quantity  of  air  would  be  sufficient  to  destroy  the  carbon-filament.  The 
plaster  at  the  base  of  the  lamp  is  merely  for  the  purpose  of  attaching  the  glass 
to  the  threaded  metal  cap,  by  which  it  is  held  in  an  electrolier  or  bracket.] 


THE  EDISON   LAMP. 


169 


Thus  constructed,  the  Edison  lamps  are  adapted  to  all 
decorative  appliances  which  we  have  been  in  the  habit  of 
using  in  our  houses ;  they  can  be  arranged  on  lusters  (Fig. 
108)  as  well  as  candles  ;  porcelain  shades  can  be  placed  over 
them  (Fig.  109);  they  can  be  mounted  on  long,  jointed  brackets 


FIG.  113.— Edison  mining-lamp. 

like  gas-brackets  (Fig.  110) ;  they  can  be  arranged  for  the  work 
of  a  study  (Fig.  Ill),  or  the  lighting  of  a  luxurious  parlor 
(Fig.  112). 

It  is  even  easy  to  place  them  in  bronze  vases  or  artistically 
designed  pieces  of  faience,  imitating  oil-lamps,  and  when  sur- 
rounded by  a  globe  the  illusion  is  perfect.  It  is  true  that  then 


170  THE  INCANDESCENT  LIGHT. 

a  little  light  is  lost.  [The  lamp  has  also  been  adapted  to  use 
in  dangerous  mines.  The  construction  for  this  purpose  is 
shown  in  Fig.  113.  The  circuit  is  made  and  broken  under 
mercury  &,  #,  contained  in  the  glass  tubes  C,  D,  secured  to 
the  block  B.  The  mercury  is  covered  with  a  layer  of  water 
5,  5,  and  the  whole  apparatus  placed  in  the  glass  jar  A.] 

Mr.  Edison's  system  of  lighting  is  completed  by  special 
dynamo-electric  machines,  of  which  we  shall  speak  later,  in 
the  fourth  book,  and  by  an  electrical  distribution,  which  will 
be  explained  in  the  fifth  book.  This  distribution  has  been 
long  experimented  with  at  Menlo  Park,  in  the  village  where 
the  inventor  resides,  and  he  is  about  establishing  it  in  JSTew 
York,  in  the  first  district  of  the  city.  [This  station  was  put 
in  operation  in  September,  1882.] 


CHAPTER  V. 

THE  SWAN,  MAXIM  AND  LANE-FOX  LAMPS. 

THE  Edison  lamp  is  not  the  only  one  using  a  carbon-fila- 
ment in  a  vacuum.  It  has  sisters  resembling  it  greatly,  and 
forms  with  them  a  distinctly  characterized  family.  It  is  far 
from  rash  to  suppose  that  this  family  will  increase  by  the 
addition  of  new  members  in  a  time  more  or  less  remote.  At 
the  present  moment  there  are  at  least  three  other  lamps  which 
ought  to  attract  our  attention  by  their  ingenious  arrangement 
of  parts,  and  the  extensive  use  which  they  have  attained  out- 
side of  France.  These  are  the  Swan,  Lane-Fox,  and  Maxim 
lamps — the  first  two  English  in  origin  ;  the  last,  like  that  of 
Edison,  American  in  origin. 

I.  THE  SWAN  LAMP. 

While  giving  above  the  history  of  incandescence,  we  indi- 
cated the  rock  upon  which  the  first  lamps  with  carbon-pen- 
cils, invented  by  the  Russian  savants,  between  1873  and  1876, 
stranded.  The  carbon-strip,  which  had  to  be  cut  very  thin 
to  " strangle"  the  current,  grew  thin  toward  its  middle,  by 
the  action  of  the  current,  and  soon  ended  by  breaking.  The 
inventors  directed  all  their  efforts  toward  the  discovery  of 


THE   SWAN,   MAXIM,   AND   LANE-FOX  LAMPS.  171 

an  unbreakable  pencil,  and  it  was  in  the  midst  of  these  ex- 
periments and  laborious  researches  that  the  open-air  incan- 
descent lamp  was  invented  in  France,  by  M.  Reynier. 

Among  those  who  studied  the  same  problem  in  England 
was  a  merchant  of  Newcastle,  known  already  by  several  meri- 
torious works  on  chemistry,  Mr.  Swan.  He  had  already  tried, 
fifteen  years  before,  to  construct  an  incandescent  lamp  with  a 
small  spiral  of  carbonized  paper,  which  he  placed  between  the 
two  blocks  of  carbon,  in  the  interior  of  a  glass  tube,  where  he 
had  created  a  vacuum  by  pumping  out  the  air,  using  the 
crude  means  then  at  the  experimenter's  disposal.  The  carbon 
grew  red,  but  did  not  reach  the  elevated  temperature  of  white 
heat,  which  alone  can  convert  it  into  a  true  source  of  light ; 
but  it  none  the  less  was  disintegrated,  casting  upon  the  walls 
of  the  glass  tube  carbonaceous  particles  which  soon  obscured 
them. 

The  principal  cause  of  this  want  of  success  was  the  imper- 
fect vacuum  obtained.  But,  in  1877,  the  wonderful  experi- 
ments of  Mr.  Crookes  upon  light  in  a  vacuum  showed  that 
much  more  efficacious  action  could  be  obtained  with  a  Spren- 
gel  mercury-pump.  Mr.  Swan  took  up  his  studies  anew,  in 
collaboration  with  Mr.  Stearns,  of  Birkenhead,  almost  at  the 
same  time  that  Mr.  Edison  attacked  the  same  problem  in 
America  with  that  energy  which  the  Yankees  bring  into  all 
their  work. 

Thanks  to  the  Sprengel  pump,  the  vacuum  was  more  per- 
fect, and  the  lamp  did  better,  without  working  perfectly  by 
any  means,  because  the  carbon  soon  became  disintegrated. 

We  have  seen  that  this  was  due  to  the  fact  that  carbon, 
like  most  other  bodies,  and  even  more  than  others,  occluded 
in  its  pores  a  considerable  quantity  of  air  and  of  other  gases, 
which  the  disturbance  produced  by  the  current  slowly  set  at 
liberty.  A  double  inconvenience  resulted  from  this  :  the  more 
perfect  the  vacuum  that  was  obtained,  the  more  the  cohesion 
of  the  carbon  was  injured  by  these  internal  gaseous  ebullitions. 

The  remedy  was  perfectly  clear :  it  was  to  bring  the  carbon 
to  incandescence  while  the  vacuum  was  being  produced,  and 
to  repeat  the  operation  several  times,  to  completely  free  it  of 
all  its  gaseous  guests.  The  filaments  of  carbon  subjected  to 
this  prolonged  treatment  became  greatly  modified  ;  they  grew 
very  much  harder,  and  acquired  an  elasticity  that  they  would 
hardly  have  been  deemed  capable  of. 


172 


THE   INCANDESCENT  LIGHT. 


An  analogous  fact  had  already  been  proved  by  Mr.  Edison 
in  the  case  of  platinum.  It  may  be  supposed  that  his  experi- 
ments, already  known  to  the  world,  had  shown  Mr.  Swan  the 
road  to  be  followed  in  his  studies  of  carbon. 

It  was  only  at  the  end  of  the  year  1880  that  Mr.  Swan  suc- 
ceeded in  giving  his  carbon-thread  the  solidity  that  character- 
izes it  to-day,  and  on  October  20th  he  presented  his  lamp  to 
the  Philosophic  and  Literary  Society  of  Newcastle.  The  car- 
bon-filament is  now  made  out  of  cotton  thread,  which  is  bent 
into  a  horseshoe- shape  with  a  spiral  turn  in  its  middle.  These 
cotton  tresses  are  subjected  to  numerous  oper- 
ations before  being  used  in  the  lamps. 

They  are  first  plunged  into  sulphuric  acid, 
diluted  with  one  third  part  of  water,  which 
makes  them  hard  like  parchment ;  they  are 
then  placed  in  charcoal-dust,  which  is  heated 
to  orange  heat.  Leaving  this,  they  are  placed 
in  the  lamp — a  simple  bulb  of  transparent 
glass,  of  eight  centimetres  in  diameter — and 
a  vacuum  is  produced  in  this  lamp  with  a 
Sprengel  mercury-pump,  while  the  electric  cur- 
rent is  kept  passing  through  the  filaments  of 
carbonized  cotton  for  a  full  half -hour.  Final- 
ly, the  lamp,  which  has  a  stem  six  centimetres 
long,  traversed  by  the  two  platinum  wires  that 
carry  the  current  to  the  carbon-filaments,  is 
sealed  (Fig.  114). 

Nothing  further  is  necessary  but  to  force 
the  stem  of  the  lamp  into  a  candlestick,  as  is 
done  with  a  candle,  when  it  will  at  once  be 
ready  for  action.  This  candlestick  receives  the  electric  cur- 
rent by  wires,  which  do  not,  however,  prevent  it  from  being 
moved,  within  a  certain  radius,  with  much  more  facility  than 
a  gas-lamp  with  its  caoutchouc  tube  (Fig.  11'5). 

Instead  of  being  held  by  a  candlestick,  incandescent  lamps 
can  be  placed  in  candelabra,  lusters,  brackets,  or  in  ordinary 
lamps  in  place  of  an  oil-burner.  They  all  have  more  than 
double  the  intensity  of  an  ordinary  Carcel  lamp,  and  it  is 
easy  to  have  them  weaker  if  it  be  desired.  For  this  the 
length  of  the  incandescent  filament  must  be  diminished,  or 
the  intensity  of  the  current  reduced  ;  but  this  second  means 
is  not  so  easy,  while  with  the  first  there  is  no  difficulty  in 


FIG.  114.— Swan 
incandescent  lamp. 


THE   SWAN,   MAXIM,   AND  LANE-FOX   LAMPS. 


173 


having  at  the  one  time  lamps  of  all  degrees  of  intensity,  like 
gas-burners,  colza  or  petroleum  lamps,  candles,  and  tapers. 


FIG.  115. — Swan  table  lamp. 

To  light  or  extinguish  the  lamp,  it  is  enough  to  turn  a  little 
electrical  cock — that  is  to  say,  a  key  placed  in  the  base  of  the 
apparatus  (Fig.  116),  and  which  opens  or  closes  the  circuit. 


174 


THE   INCANDESCENT  LIGHT. 


[In  the  later  form  of  this  lamp  the  bulb  is  reduced  in  size  and 
the  neck  much  shortened.  The  mounting  is  elastic  and  of  ex- 
treme simplicity  (Figs.  117  and  118).  The  outer  ends  of  the 

platinum  leading  wires,  a,  a', 
are  bent  so  as  to  form  eyes 
into  which  hook  the  ends  of 
the  circuit  wires,  &,  U.  A 
stout  spiral  spring,  R,  insures 
a  perfect  contact  between 
them  while  allowing  consid- 
erable freedom  of  movement.] 
This  system,  it  will  be 
seen,  also  furnishes  a  com- 
plete solution  of  the  problem 
of  domestic  lighting,  and  can 
supplant  gas  or  oil  in  almost 


FIG.  116.— Under  side  of  the  foot  of  the  lamp, 
showing  the  electrical  connections. 


all  their  accustomed  places, 
provided  always  that  there 
be  established  in  the  streets  a  distributing  system  of  elec- 
tricity similar  to  that  used  at  the  present  day  for  gas. 


FIG.  117. — Swan  lamp.    Later  form. 


FIG.  118.— Swan  lamp  in  socket. 


Mr.  Swan  has  not  touched  upon  this  question  ;  herein  his 
system  is  less  complete  than  that  of  Mr.   Edison,  who  has 


13 


176 


THE   INCANDESCENT  LIGHT. 


provided  for  everything.  Mr.  Swan  has  not  yet  had  time  to 
design  dynamo-electric  machines  specially  adapted  to  supply 
his  lamps.  He  has  no  preference  for  any  particular  form  of 
generator. 

Nevertheless,  the  lamp  of  Mr.  Swan  is  now  used  in  Eng- 
land in  a  great  many  places.  In  Newcastle,  the  home  of  the 
inventor  (Fig.  119),  it  lights  several  streets.  Mr.  William 
Spottiswoode,  President  of  the  Royal  Society  of  London,  has 

placed  it,  along  with  Jabloch- 
koff  candles,  in  his  large  resi- 
dence of  Coombes-Bank ;  and 
the  great  metal-worker,  Sir 
William  Armstrong,  has  also 
established  it  in  his  house. 

One  of  the  railroad  com- 
panies of  England  employs  it 
to  light  its  cars,  to  the  great 
satisfaction  of  travelers,  who 
can  read  with  pleasure.  It 
has  also  been  successfully 
tried  in  mines,  with  a  special 
model  surrounded  with  wa- 
.  T  mi  *er'  an^  therefore  incapable 

of    igniting    the    fire-damp, 
I     R  W/4/w!  even  in  case  of  breakage  of 

\    l\  /\  the  aPParatus  (Fig- 120)-    Fi~ 

^  'I  nally,    it  has   been   used   in 

submarine  operations  with 
sounding  apparatus. 

We  cite  these  different  ex- 
amples as  proof  of  the  many 
applications  already  in  use. 

FIG.  120.— Swan  mining-lamp.  Many  others  can  be  added, 

because,  at  the  present  time, 

the  Swan  lamp  is  the  most  used  of  all  incandescent  lamps  in 
actual  practice — that  is  to  say,  in  paying  operation. 

The  thread  of  incandescent  carbon  is  a  little  thicker  in  the 
Swan  lamps  than  in  Edison's,  and  consequently  their  lumi- 
nous power  is  a  little  greater  when  they  receive  a  current  of 
sufficient  intensity  ;  but  it  is  well  understood  that  they  need 
more  of  it  to  attain  the  same  degree  of  luminosity,  that  of 
white  heat.  The  inventor  hoped  to  guarantee  an  illuminating 


THE   SWAN,   MAXIM,   AND   LANE-FOX  LAMPS. 


177 


UNIVERSITY 


power  of  twenty  English  candles,  which  is  more  than 
Carcel  lamps,  and  he  affirms  that  under  these^ 
horse-power  would  suffice  for  ten  lamps. 

II.  THE  LANE-FOX  LAMP. 

The  lamp  of  Mr.  Lane-Fox  (Fig,  121),  of  EnglisB^rT[ 
like  that  of  Mr.  Swan,  resembles  it  a  great  deal  in  its  exterior 
form  and  dimensions.    It  is  also  formed  of  a  very  thin  carbon- 
filament,  bent  into  the  shape  of  an  elongated  horseshoe,  but 
without  a  central  spiral ;  this  thread 
is  in  the  same  manner  placed  in  a  glass 
bulb,  where  the  best  vacuum  possible 
is  made.     Nevertheless,  the  lamp  of 
Mr.  Lane-Fox  differs  from  that  of  his 
compatriot  by  two  principal   points, 
and  those  quite  important,  which  we 
shall  examine  in  succession. 

The  thread  of  carbon,  destined  to 
become  incandescent,  has  neither  the 
same  origin  nor  the  same  nature.  Gen- 
erally it  is  a  fiber  of  couch-grass,  car- 
bonized with  special  precautions.  The 
carbon  becomes  just  as  hard  as  that 
of  Mr.  Swan,  and  is,  in  the  same  way, 
deprived  of  the  air  hidden  in  its  pores, 
thanks  to  the  same  precaution ;  it  is 
kept  incandescent  while  the  vacuum 
is  forming. 

Instead  of  creating  the  vacuum  by 
aid  of  the  Sprengel  pump,  Mr.  Lane- 
Fox  prefers  a  method  analogous  to 
that  which  is  in  use  in  France  by  M. 

Alvergniat,  for  the  manufacture  of  Geissler  tubes,  in  which 
light  produces  such  beautiful  effects  in  different  gases.  This 
method  consists,  briefly,  in  obtaining  the  same  vacuum  as 
exists  above  the  mercury  in  a  barometer,  in  what  is  called 
the  barometric  chamber.  But  ingeniously  devised  precau- 
tions are  taken  to  keep  the  atmosphere  free  from  mercury- 
vapor,  which  ordinarily  would  fill  this  chamber. 

Mr.  Lane-Fox's  lamp  is  further  characterized  by  the  man- 
ner in  which  the  thread  of  incandescent  carbon  is  attached  to 


FIG.  121.— Lane-Fox  incan- 
descent lamp. 


178 


THE  INCANDESCENT  LIGHT. 


Wooden  cup 


the  metallic  wires  which  conduct  the  electric  current  to  it. 
Instead  of  being  thickened  as  it  approaches  the  points  of  con- 
tact, like  the  filament  of  Mr.  Swan,  the  filament  of  Mr.  Lane- 
Fox  preserves  the  same  diameter.  But  the  two  extremities 
are  fastened  in  the  axis  of  two  small  plumbago  cylinders, 
where  they  join  platinum  wires  relatively  large,  which  at 

their  other  ends  are  attached 
to  the  ordinary  copper  con- 
ducting wire. 

[To  prevent  undue  heating 
of  the  leading- wires,  these  lat- 
ter are  fused  into  small  pil- 
lars of  glass,  the  lower  ends 
of  which  are  expanded  into 
small  globes  containing  mer- 
cury. The  platinum  wires  dip 
into  these,  as  also  the  copper 
leads  which  serve  to  make 
electrical  connection  with  the 
circuit  upon  which  the  lamp 
is  placed.  The  mercury  is  re- 
tained in  place  by  a  filling  of 
marine  glue,  and  over  this  a 
plug  of  plaster.  The  dispo- 
sition of  parts  is  shown  in 
Fig.  122,  in  which  c  c  are  the 
mercury  reservoirs,  and  b  b 
the  glass  pillars  in  which  the 
platinum  leads  are  sealed. 
The  globe  and  this  stem,  with 

the  wires  mounted  in  it,  are  joined  together  at  the  base  of  the 
neck  of  the  former  by  fusion,  as  in  the  case  of  the  two  pre- 
vious lamps.] 

Mr.  Lane-Fox,  like  Mr.  Swan,  has  arranged  no  system  for 
distribution  or  production  of  electricity.  But  he  has  invented 
an  apparatus  which  automatically  regulates  the  intensity  of 
the  current,  and  keeps  it  almost  constant  at  the  wished-for 
point,  or  at  least  restrains  its  variations  within  certain  limits, 
without  the  necessity  of  any  attention. 

This  automatic  regulator  works  under  the  action  of  the 
same  current  that  goes  through  the  lamps,  like  the  regulator 
of  voltaic-arc  lamps,  and  it  is  mounted  on  a  special  derived 


FIG.  122. — Section  of  Lane-Fox  lamp. 


THE  SWAN,   MAXIM,   AND  LANE-FOX  LAMPS. 


179 


circuit ;  only,  instead  of  bringing  the  carbon-rods  together,  it 
interposes  in  the  path  of  the  current,  at  the  right  moment 
and  in  proper  quantity,  resistance  apparatus,  which  increase 
the  resistance  of  the  circuit,  and  consequently  diminish  the 
force  of  the  current  which  finally  passes  through  it. 

The  lamps  of  the  Lane-Fox  system  are  less  employed  here 
(in  France)  than  the  other  incandescent  lamps,  and  we  know 
of  no  applications  of  them  of  sufficient  importance  to  be 
worth  describing.  The  truth  is,  that  no  company  has  been 
organized  to  introduce  them. 


III.  THE  MAXIM  LAMP. 

[The  lamp  of  Mr.  Hiram  S.  Maxim  has  the  same  general 
features  of  those  above  described.  The  filamentary  con- 
ductors are  stamped  from  paper,  and  have  the  form  of 
the  letter  M,  instead  of  a  simple  loop.  They  are  carbonized 
between  sheets  of  paper  in 
iron  molds,  and  are  after- 
ward subjected  to  a  treat- 
ment to  render  them  as  ho- 
mogeneous as  possible.  Mr. 
Edison  abandoned  paper  as 
a  material  for  his  incandes- 
cent filaments  because  of 
the  difficulty  of  getting  it 
homogeneous.  Mr.  Maxim 
endeavored  to  overcome  this 
defect  by  heating  the  fila- 
ments to  incandescence  in 
a  carbonaceous  atmosphere. 
The  gas  is  decomposed  by 
the  heat  of  the  filament, 
and  the  liberated  carbon 
deposited  upon  it,  those 
parts  which  are  thinnest, 

and     consequently    hottest,  Flo.  i23.-Maxim  incandescent  lamp, 


^ 

receiving  the   heaviest  de- 
posit. 

Filaments  of  very  uniform  conductivity  can  be  produced 
in  this  manner,  and  any  form  of  carbon  can  be  so  treated.  A 
rarefied  atmosphere  of  gasoline-vapor  is  that  usually  employed, 


180 


THE  INCANDESCENT  LIGHT. 


and  the  deposit  is  commonly  made  in  a  separate  vessel  before 
the  filament  is  mounted  for  sealing  in  the  final  globe,  though 
it  can  be  readily  effected  while  the  lamps  are  on  the  mer- 
cury-pump before  the 
final  exhaustion  is  com- 
pleted. This  method  of 
equalizing  the  resistance 
of  a  filament  is  also  used 
by  Lane -Fox,  and  an 
analogous  one  was  em- 
ployed by  Sawyer  and 
Mann. 

The  platinum  leading 
wires  are  attached  to  the 
filament  by  a  species  of 
clamp.  The  ends  of  the 
filament  are  enlarged, 
as  are  also,  those  of  the 
leading  wires.  The  two 
are  then  clamped  togeth- 
er by  means  of  a  minute 
bolt  provided  with  a  nut 
passing  through  each — 
a  remarkably  expensive 
mode  of  attachment. 
The  leading  wires  are 
sealed  into  the  glass  of 
the  globe,  as  in  the  oth- 
er lamps  of  this  kind. 
The  appearance  of  the 
complete  lamp  is  shown 
in  Fig.  123,  and  the  lamp 

FIG.  124.-Maxim  incandescent  lamp  and  socket.          m<>Unted    in    its    SOCket, 
(Full  size).  in  Fig.   124.] 


IV. 


LAMPS. 


[Lamps  of  the  same  general  character  as  these,  but  differing 
from  each  other  in  the  mode  of  manufacture  of  the  filament, 
of  mounting  it  upon  the  leading  wires,  and  of  sealing  these 
latter  into  the  inclosing  globe,  have  been  designed  by  various 
other  inventors,  but  they  do  not  call  for  a  description  here. 


THE   SWAN,    MAXIM,   AND   LANE-FOX  LAMPS. 


181 


Two  new  lamps  have,  however,  recently  been  brought  to 
public  notice  which  deserve  mention.  One  is  of  American 
origin,  the  invention  of  Mr.  Alexander  Bernstein ;  and  the 
other  is  an  Italian  invention,  devised  by  Signor  Antonio  Cruto. 
In  the  first  of  these  the  light-giving  portion  consists  of  a 
small  tube  of  carbon,  instead  of  the  fine  carbon  wire  of  the 
lamps  described  above.  It  is  mounted  upon  platinum  leading 
wires,  and  inclosed  in  an  exhausted  glass  globe,  as  in  other 
incandescent  lamps.  The  carbon  cylinders  were  first  made 
by  carbonizing  straws,  and  later  by  depositing  carbon  upon 
a  metallic  wire  and  afterward  dissolving  the  metal  out.  Both 
of  these  methods  were  finally  aban- 
doned, and  the  tubes  produced  by 
rolling  paper  about  a  metal  mandrel, 
the  successive  layers  of  paper  being 
made  to  adhere  by  means  of  gum  or 
paste.  The  whole  was  then  carbon- 
ized in  a  mold  from  which  the  air  was 
excluded.  The  shrinkage  of  these 
paper  tubes  during  carbonization  was 
very  great,  and  paper  was  therefore 
replaced  by  finely  woven  cotton  or 
silk  fabric.  The  earlier  carbons  were 
made  straight,  but  it  has  been  found 
possible  to  produce  the  tubes  in  the 
form  of  an  arch,  and  the  present  lamp 
is  therefore  constructed  with  a  curved 
carbon.  It  is  represented  in  Fig.  125. 
These  carbon  tubes  are  said  to  be  ex- 
tremely elastic,  so  much  so  that  they 
can  be  drawn  out  nearly  straight,  and 
will  spring  back  to  their  normal  shape.  The  lamp  differs 
from  those  previously  made  in  being  of  very  low  resistance. 
It  is  therefore  not  suitable  for  distribution  on  a  large  scale, 
but  will  answer  well  enough  for  separate  installation,  such 
as  those  of  a  shop  or  store. 

In  the  first  descriptions  of  the  lamp  of  Signor  Cruto,  the 
incandescent  organ  was  said  to  be  a  fine  carbon  tube,  formed 
by  depositing  carbon  upon  a  platinum  wire  heated  to  incan- 
descence while  immersed  in  oil,  and  then  dissolving  out  the 
platinum.  It,  however,  appears  from  later  descriptions  that 
the  platinum  is  not  removed,  so  that  the  light-giving  portion 


FIG.  125.— The  Bernstein  lamp. 


182 


THE  INCANDESCENT  LIGHT. 


is  really  a  compound  filament,  consisting  of  a  platinum  core 
and  carbon  exterior.  This  lamp  was  exhibited  at  the  Munich 
Exhibition  in  1882,  and  that  at  Vienna  last  year,  but  has  not 
yet  made  its  appearance  in  this  country.] 


CHAPTER  VI. 

MEASUREMENT  OF  INCANDESCENT  LAMPS. 

[To  measure  an  electic  lamp  two  quantities  must  be  deter- 
mined— the  electrical  work  done  per  second  to  maintain  the 
light,  and  the  candle-power.  The  first  of  these  is  equal  to 
E  C,  the  product  of  the  difference  of  potential  between  the 
terminals  of  the  lamp,  by  the  intensity  of  the  current  flowing 
through  it.  The  difference  of  potential  is  generally  measured 
directly,  but  the  current  can  be  more  accurately  determined 
by  measuring  the  resistance,  and  then  calculating  it  from  the 

E 

equation  C  =  -,  which  is  the  method  pursued  in  the  case  of 
K 

small  currents  such  as  those  through  incandescent  lamps. 
This  resistance  must  be  measured  while  the  lamp  is  burning 
at  the  desired  candle-power,  as  it  changes  with  the  tempera- 
ture, becoming  less  in  the  case 
of  carbon  and  greater  in  that 
of  metals,  as  the  temperature 
is  raised.  It  will  not  be  ne- 
cessary to  enter  here  upon  a 
consideration  of  the  details  of 
the  methods  and  instruments 
of  electrical  measurements,  but 
only  to  indicate,  in  a  general 
way,  how  the  electro -motive 
force  and  resistance  are  de- 
termined. To  measure  resist- 
ance an  arrangement  termed  a 

Wheatstone  bridge  (shown  in  Fig.  126)  is  generally  used. 
Its  action  depends  upon  the  regularity  of  the  fall  of  poten- 
tial throughout  a  circuit.  If  the  two  ends  of  a  wire  are  at 
different  potential,  a  point  at  the  center  of  the  wire  will  be 


FIG.  126.— Wheatstone' s  bridge. 


MEASUREMENT  OF  INCANDESCENT  LAMPS.  183 

at  a  potential  equal  to  half  that  of  the  ends,  and  generally 
a  point  anywhere  between  the  two  ends  will  have  a  potential 
depending  on  its  position.  Further,  a  current  will  only  flow 
through  a  wire  when  there  is  a  difference  of  potential  between 
its  ends.  In  the  figure  the  current  enters  at  A,  and  divides 
between  the  two  circuits  ADC  and  ABC.  If  these  be  joined 
by  a  cross-wire,  no  current  will  flow  through  this  wire  when 
its  ends  are  at  the  same  potential.  This  will  be  the  case  when 
the  resistance  x  is  to  the  resistance  R.  as  the  resistance  s  is  to  S. 

A 

From  this  we  have  the  unknown  resistance  x  =  R  — .     A 

o 

galvanometer  placed  in  this  cross-circuit  indicates  the  pres- 
ence of  a  current  through  it  by  the  deflection  of  its  needle. 
In  the  practical  form  of  this  apparatus  the  resistances  s  and  S 

a 

are  taken  of  such  values  that  the  ratio  —  may  vary  from  y^ 

o 

of  an  ohm  up  to  100  ohms.  When  this  ratio  equals  1,  the  re- 
sistance to  be  measured,  a?,  is  evidently  equal  to  the  adjustable 
resistance  B,. 

The  most  accurate  way  of  determining  a  difference  of  po- 
tential is  by  the  use  of  a  condenser — an  apparatus  consisting 
of  a  number  of  sheets  of  tin-foil,  separated  from  each  other 
by  means  of  paraffined  paper,  or  mica,  of  which  a  familiar 
example  is  the  Leyden-jar. 
The  charge  of  electricity  re- 
ceived by  a  condenser  will  be 
proportional  to  the  electro- 
motive force  of  the  charging 
current.  To  use  it  in  measur- 
ing the  electro-motive  force 
of  an  electric  lamp,  it  is  first 
charged  by  a  source  of  elec- 
tricity of  known  electro-motive 

force,   SUCh  as   a  Standard  Cell,  FIG.  127.— Bunsen  photometer. 

and  then  discharged  through 

a  galvanometer  and  the  deflection  of  the  needle  noted.  The 
terminal  wires  are  then  connected  with  the  terminals  of  the 
lamp,  and  again  discharged  through  the  galvanometer.  This 
second  deflection  will  then  give  the  electro-motive  force  of 
the  lamp-current  in  terms  of  the  standard,  and  if  this,  as  is 
usually  the  case,  is  unity,  directly  in  volts. 

The  intensity  of  any  light  is  determined  by  comparing  it 


184 


THE  INCANDESCENT  LIGHT. 


to  a  standard  candle.  A  number  of  different  photometers,  as 
the  instruments  for  making  this  comparison  are  called,  have 
been  devised,  but  that  most  largely  used  is  the  one  invented 
by  Bunsen.  The  operation  depends  upon  the  action  of  trans- 
mitted and  reflected  light.  If  a  grease  spot  be  made  on  a 
sheet  of  paper,  the  spot  will  appear  darker  than  the  surround- 
ing surface  when  the  light  is  in  front  of  the  paper,  and  lighter 


FIG.  128. — Method  of  using  the  Bunsen  photometer. 

when  behind  it.  If  the  paper  be  equally  illuminated  on  both 
sides,  the  spot  will  be  indistinguishable  from  the  rest  of  the 
sheet.  In  the  actual  instrument  the  paper  is  mounted  in  a 
dark  box,  generally  sheet-iron  painted  black,  being  placed 
across  the  length  of  the  box,  through  each  end  of  which  the 
rays  from  the  lights  enter.  Two  inclined  mirrors  are  placed 
so  that  they  meet  at  the  back  edge  of  the  paper  disk,  as 


MEASUREMENT   OF  INCANDESCENT  LAMPS. 


185 


shown  in  Fig.  127.  The  eye  of  the  observer  is  placed  in 
front,  so  that  the  reflection  of  the  spot  in  .the  mirrors 
is  seen.  When  the  reflections  disappear,  the  two  sides  of 
the  paper  disk  are  equally  illuminated,  and  the  relative 
intensities  of  the  lights  are  to  each  other  as  the  squares  of 
their  distances  from  the  disk.  The  dark  box  is  mounted 
upon  rollers,  so  that  it  can  be  readily  moved  between  the 
two  lights  along  a  track,  which  is  commonly  graduated  to 
give  at  once  the  intensity  of  the  light  being  measured.  Two 
candles  are  generally  used  as  a  standard  instead  of  one. 
The  whole  apparatus  is  inclosed  in  a  dark  chamber,  as 
shown  in  Fig.  128. 

A  great  many  tests  of  the  performance  of  incandescent 
lamps  have  been  made  in  the  past  few  years,  but  it  will  suf- 
fice to  give  here  the  results  obtained  by  the  committees  at 
the  International  Exhibition  at  Paris  in  1881,  and  at  Munich 
in  1882.  The  lamps  examined  by  the  Paris  committee  were 
those  of  Edison,  Maxim,  Swan,  and  Lane-Fox.  They  were 
measured  at  sixteen  and  thirty-two  candles,  with  the  re- 
sults given  in  the  following  tables  : 

At  Sixteen  Candles. 


LAMPS. 

Edison. 

Swan. 

Lane-  Fox. 

Maxim. 

Candles  

15-38 

16-61 

16-36 

15-96 

Ohms. 

137-4 

32'78 

27-40 

41-11 

Volts  

89-11 

47-30 

43-63 

56-49 

Amperes  

0-651 

1-471 

1-593 

1-380 

Volt-amperes  

57'98 

69-24 

69-53 

78-05 

Kilogramme-metres 

5-911 

7-059 

7-089 

7-939 

Lamps  per  horse-power  

12-73 

10-71 

10-61 

9-48 

Candles  per  horse-power 

196-4 

177-92 

173-58 

151-27 

Lamps  of  sixteen  candles  per  horse-power.  . 

12-28 

11-12 

10-85 

9'45 

At  Thirty -two  Candles. 


LAMPS. 

Edison. 

Swan. 

Lane-Fox. 

Maxim. 

Candles  

31-11 

33-21 

32-71 

31-93 

Ohms.  .  . 

1  30-03 

31-75 

26-59 

39-60 

Volts 

98-39 

54.21 

48-22 

62-27 

Amperes    .         

0*7585 

1-758 

1-815 

1-578 

Volt-amperes 

74-62 

94-88 

87'65 

98-41 

Kilogramme-metres  ... 

7-604 

9-67 

8-936 

10-03 

Lamps  per  horse-power  

9-88 

7-90 

8-47 

7*50 

Candles  per  horse-power.  .               

307-25 

262-49 

276-89 

239-41 

Lamps  of  thirty-two  candles  per  horse-power.  .  .  . 

9-60 

8-20 

8-65 

7-48 

186 


THE  INCANDESCENT   LIGHT. 


The  lamps  examined  by  the  Munich  committee  were  the 
Edison,  Maxim,  Swan,  Siemens,  and  Cruto.  The  results  are 
given  in  the  following  table  : 

Results  of  the  Munich  Committee. 


LAMPS. 

Mean  spherical 
luminous  in- 
tensity in  nor- 
mal candles. 

Resistance  when 
hot,  in  ohms. 

Difference  of  po- 
tential, in  volts. 

i 

i* 

ELECTRICAL 
WOKK  IN 

Mean  spherical 
intensity  per 
horse-power. 

Number  of  lamps 
per  horse-power. 

Volt-am- 
peres. 

II 

Edison  B  

11-69 
15-32 
13-34 
10-95 
37-17 
14-90 
18-43 
43-08 
102-35 
8-47 

67-68 
139-60 
47-01 
31-91 
87-03 
104-72 
58-62 
59-52 
6541 
8-16 

55-78 
103-05 
65-07 
38-38 
118-02 
95-74 
74-04 
105-22 
155-15 
22-15 

0-825 
0-755 
1-384 
1-222 
1-282 
0-915 
1-263 
1-779 
2-367 
2-715 

46-02 
77-80 
90-06 
46-90 
151-30 
87-60 
93'51 
187-19 
367-24 
60-14 

0-0625 
0-1057 
0-1224 
0-0637 
0-2056 
0-1191 
0-1271 
0-2544 
0-4991 
0-0817 

186-90 
144-88 
108-98 
171-78 
180-75 
125-14 
145-01 
169-33 
205-05 
103-58 

23-36  (8  candles) 
9-05  (Ifi           ) 
3-89  (28           ) 
17-18  (10           ) 
4-52  (40           ) 
7-82  (16           ) 
7-26  (20           ) 
3-39  (50     "     ) 
2-05  (100  "     ) 
10-36  (10     "     ) 

"      A 

Maxim  
Swan  A  

"      B  .. 

Siemens  

Miiller  A 

"     B 

"     C         

Cruto 

In  each  of  these  tables  the  results  are  expressed  in  French 
horse-power,  which,  it  will  be  remembered,  is  equal  to  735*75 
volt-amperes  or  watts.  To  obtain  the  number  of  lamps  in 
English  horse-power,  it  is  necessary  to  divide  746  by  the  volt- 
amperes  in  the  table. 

These  two  sets  of  measurements  are  not  directly  compar- 
able, as  the  candle-power  in  the  first  is  obtained  by  a  horizon- 
tal measurement  at  an  angle  of  45°  to  the  plane  of  the  loop, 
and  in  the  second  it  is  averaged  so  as  to  be  the  same  in  all 
directions. 

This  latter  method  of  expressing  the  candle-power  places 
the  incandescent  lamp  at  a  disadvantage  with  gas,  the  illumi- 
nant  with  which  it  is  directly  compared  in  all  discussions  of 
its  use  in  general  lighting,  while  it  does  not  possess  any  ad- 
vantage in  the  matter  of  accuracy.  It  would  seem  to  be  bet- 
ter to  adhere  to  the  established  practice  in  gas  measurements, 
which  is  to  measure  the  flat  flame  horizontally,  at  right  angles 
to  its  plane. 

The  Munich  report  is,  moreover,  obviously  erroneous  in  the 
method  of  obtaining  the  number  of  lamps  per  horse-power. 
For  instance;  the  table  exhibits  a  great  discrepancy  between 
the  economy  of  the  Edison  eight  and  sixteen  candle  lamps. 


EFFICIENCY   OF  THE  INCANDESCENT  LAMP.  187 

The  reason  of  this  is,  however,  readily  apparent  on  finding  that 
the  eight  candle  lamp  was  measured  at  11  *69  candles,  a  much 
more  economical  incandescence  than  its  normal  one,  while  the 
sixteen  candle  lamp  was  measured  at  15*32  candles,  a  some- 
what less  economical  incandescence  than  the  normal.  In  sev- 
eral other  cases  lamps  are  measured  at  an  incandescence  con- 
siderably above  or  below  the  standard  to  which  it  is  reduced 
in  the  last  column.  The  consideration  adduced  in  Chapter 
VII  of  this  book  will  enable  the  reader  to  understand  why 
such  a  procedure  is  not  permissible. 

Neither  of  these  tests,  moreover,  shows  the  performance  of 
the  latest  lamps.  The  carbon-filament  has  been  steadily  im- 
proved, and  the  present  lamps  are  consequently  more  eco- 
nomical. No  official  tests  have,  however,  been  made  of  these.] 


CHAPTER  VII. 

CONDITIONS  OF  EFFICIENCY  IN  THE  INCANDESCENT  LAMP. 

[!F  a  current  of  electricity  be  passed  through  a  wire  which 
offers  resistance  to  its  passage,  the  energy  of  the  current  will 
be  converted  into  heat,  and  the  temperature  of  the  wire  will 
rise.  The  limit  to  the  increase  of  its  temperature  will  evi- 
dently be  the  point  at  which  the  loss  of  heat  per  second  is 
equal  to  the  supply.  Otherwise  the  temperature  would  de- 
crease if  the  loss  were  at  a  greater  rate  than  the  supply,  and 
continue  increasing  if  it  were  at  a  less  rate.  It  might  at  first 
be  supposed  that  the  specific  heat  of  a  body  should  be  taken 
into  account.  But  a  moment's  consideration  will  show  us 
that  this  only  enters  as  an  element  in  determining  the  tem- 
peratures to  which  the  same  weights  of  different  substances 
will  be  elevated  by  a  definite  quantity  of  heat.  If  the  supply 
of  heat  be  continued  until  a  constant  temperature  is  at- 
tained, then  calorific  capacity  ceases  to  have  any  influence, 
and  the  amount  of  heat  lost  per  second  must  be  equal  to  that 
supplied. 

A  hot  wire  exposed  freely  to  the  air  will  lose  heat  in  three 
ways :  1,  by  radiation ;  2,  by  conduction  through  the  sup- 
ports ;  and  3,  by  convection,  through  the  medium  of  the  envel- 


188  THE   INCANDESCENT  LIGHT. 

oping  air,  the  successive  particles  of  which  become  heated  by 
contact  with  the  wire,  and  rising  give  place  to  others.  In  the 
case  of  an  incandescent  lamp,  the  filament  of  which  is  placed 
in  an  exhausted  vessel,  this  latter  source  of  loss  is  avoided. 
It  will  therefore  lose  heat  only  by  radiation  and  conduction. 
The  loss  of  heat  by  the  latter  means  will  depend  upon  the 
temperature  of  the  wire  and  its  cross-section,  while  the  loss 
by  radiation  will  depend  upon  the  temperature  and  the  sur- 
face exposed.  Neglecting  for  the  moment  the  loss  by  con- 
duction, it  is  evident  that,  to  maintain  two  wires  at  the  same 
temperature  by  the  same  expenditure  of  heat  per  second, 
these  wires  must  have  equal  surfaces,  which  will  be  the  case 
when  the  lengths  of  the  wires  are  to  each  other  inversely  as 
their  diameters.  So  far  as  radiation  is  concerned,  then,  a 
short,  thick  wire  is  as  economical  for  the  purpose  of  incan- 
descence as  a  long,  thin  one.  But  since  the  loss  of  heat 
by  conduction  through  the  supports  will  increase  with  the 
cross-section  of  the  wire,  economy  demands  that  the  wire 
be  as  thin  as  possible,  that  this  loss  may  be  reduced  to  a 
minimum. 

In  a  wire  so  circumstanced,  what  will  be  the  relation  of  its 
size  to  the  temperature  to  which  it  will  be  raised  by  a  given 
amount  of  heat  ?  Let  us  take  two  wires  of  the  same  material 
and  length,  but  of  different  diameters,  d  and  <$, ,  and  generate 
in  them  the  same  amount  of  heat  per  second — that  is,  let 
C2R  =  CJB,. 

To  maintain  the  wires  at  constant  temperatures  the  heat 
generated  in  each  per  second  per  unit  of  area  must  be,  as 
stated  above,  the  same  as  that  radiated.  By  Newton's  law  of 
cooling,  the  rates  at  which  the  wires  will  lose  heat  will  be 
directly  proportional  to  the  excess  of  their  temperatures 
above  that  of  the  inclosing  vessel.  But  the  radiation  per 
second  from  unit  surface — which  is  the  rate  of  cooling — in 
the  two  wires,  will  be  inversely  as  the  diameters  of  the  wires, 
and  we  shall  therefore  have  t :  t'=  d, :  d,  in  which  t  and  t'  are 
the  temperatures  above  those  of  the  inclosing  vessels,  to 
which  the  wires  will  be  raised.  This  law  is,  however,  accu- 
rate only  when  the  temperature  of  the  wire  is  but  slightly  in 
excess  of  that  of  the  inclosing  vessel.  Dulong  and  Petit, 
experimenting  through  a  range  of  temperature  of  from  20° 
to  240°  centigrade,  found  that  the  rate  of  cooling  was  not 
directly  proportional  to  the  excess  of  temperature,  but  that 


EFFICIENCY  OF  THE  INCANDESCENT  LAMP.  189 

it  was  greater  at  high,  than  at  low  temperatures.  They  found 
that  it  could  be  expressed  by  a  formula  of  the  form, 

H.-7i=m(ae-a6l\* 

in  which  H  is  the  total  loss  of  heat  from  unit  area  of  the 
radiating  body  per  second,  and  6  its  temperature,  while  Ol  is 
the  temperature  of  the  inclosure,  and  7i  the  amount  of  heat 
received  from  it  on  each  unit  of  area  of  the  radiating  body ; 
m  is  a  constant,  depending  upon  the  substance  and  the  nature 
of  its  surface,  and  a  a  constant,  the  value  of  which  is  1  *0077, 
when  the  temperature  is  reckoned  on  the  centigrade  scale. 
This  formula  may  evidently  be  written, 

H  -  7i  =  ma61  (a0-*1  -  1). 

The  exponent  0  —  0l  is  the  excess  of  temperature  of  the  radi- 
ating body  over  that  of  the  inclosure.  Denoting  this  by  ft, 
the  second  term  of  the  equation  becomes  mael  (a6*  —  1).  De- 
veloping aei  into  a  series,  we  have, 

««.  =  !  +  ft  loga  H-  J  (ft  loga)2  +  £  (ft  loga)3  +  etc., 
which  becomes,  on  substituting  the  numerical  value  of  loga, 

1  +  -0077ft  +  £  (-0077ft)2  +  £  (-0077ft)3  +  etc.,  and 
mael  (a6*  -I)  =  m,  1-0077'1  ^  1  +  J  (-0077ft)  4- 1  (-0077ft)2  +  etc.  ^. 

This  shows  us  that  the  radiation  from  unit  area,  instead 
of  being  directly  proportional  to  the  temperature  ft ,  is  pro- 
portional to  the  temperature  multiplied  by  a  factor  depend- 
ing on  it.  When  the  temperature  is  such  that  -0077ft  may 
be  neglected  in  comparison  with  unity,  this  factor  becomes 
practically  constant,  and  the  formula  agrees  with  Newton's 
law.f 

In  the  case  of  the  two  wires,  then,  instead  of  having  the 
temperatures  inversely  as  the  diameter  of  the  wires,  we  shall 
have  them  in  a  less  ratio,  depending  upon  the  values  of  these 
factors.  Though  the  law  of  Dulong  and  Petit  was  experi- 
mentally proved  through  only  a  small  range  of  temperature, 
it  may,  however,  be  taken  as  expressing  the  fact  that  the 
higher  the  temperature  the  more  rapid  the  radiation  of  heat. 
From  this  it  results  that  the  temperature  does  not  increase  at 
the  same  rate  as  the  generation  of  heat  necessary  to  maintain 
it.  Doubling  the  heat-expenditure  will,  therefore,  not  double 
the  temperature,  and  as  this  latter  is  increased  a  larger  and 
larger  proportional  quantity  of  heat  is  necessary  to  sustain  it. 

*  Maxwell's  "  Theory  of  Heat." 

t  Deschanel's  "Physics,"  sixth  edition.     New  York,  1883. 


190  THE   INCANDESCENT  LIGHT. 

In  our  example  of  the  wires,  if  we  take  them  of  diameters  as 
one  to  two,  by  Newton's  law  we  shall  have  the  smaller  wire 
at  twice  the  temperature  of  the  larger,  but  it  will  have  only 
one  half  the  surface  of  the  latter.  By  the  law  of  Dulong  and 
Petit  the  temperature  of  the  smaller  wire  will  not  be  twice 
that  of  the  larger,  but  something  less.  It  would  seem,  there- 
fore, that  there  is  no  advantage  in  maintaining  a  small  wire 
at  a  high,  over  a  larger  one  at  a  lower,  temperature.  And  this 
would  be  true,  if  the  light  emitted  by  an  incandescent  body 
was  directly  proportional  to  its  temperature.  But  this  is  far 
from  being  the  case. 

A  body  heated  below  977°  Fahr.  emits  only  obscure  rays 
which  affect  us  as  heat,  but  are  incapable  of  exciting  vision. 
With  an  increase  of  temperature  luminous  rays  begin  to  make 
their  appearance,  and  increase  both  in  intensity  and  amount 
as  the  temperature  is  carried  up.  This  increase  is,  moreover, 
extremely  rapid.  At  first  a  considerable  augmentation  of 
temperature  is  necessary  to  perceptibly  increase  the  light, 
but  soon  slight  additions  to  the  temperature  produce  large 
increase  of  the  light  emitted.  Experimenting  with  plati- 
num raised  to  incandescence  by  means  of  the  electric  cur- 
rent, Dr.  John  W.  Draper  found  that  the  light  emitted  and 
the  temperature  were  related  to  each  other  as  follows  : 

Temperature  of  the  Platinum.  Intensity  of  Light. 

980°  Fahr.  O'OO 

1,900  -34 

2,015  -62 

2,130  1-73 

2,245  2-92 

2,360  4-40 

2,475  7'24 

2,590  12-34 

From  which  it  appears  that  the  light  emitted  at  2,590°  was 
somewhat  more  than  thirty-six  times  that  emitted  at  a  tem- 
perature of  1,900°.  The  law  of  the  increase  of  the  light  with 
the  temperature  has  never  been  formulated,  and  I  am  not 
aware  that  experiments  have  been  carried  on  at  higher  tem- 
peratures than  those  used  by  Dr.  Draper.  The  melting-point 
of  platinum  placed  a  limit  to  the  temperature  which  he  could 
obtain,  but  with  the  incandescent  carbon-lamp  this  limit  is  so 
greatly  removed,  that  it  would  seem  to  offer  an  excellent  ex- 
perimental means  of  pursuing  this  investigation  through  a 


EFFICIENCY   OF  THE  INCANDESCENT  LAMP.  191 

sufficient  range  of  temperature  to  enable  the  relation  to  be 
definitely  formulated.  The  results,  however,  could  at  best  be 
only  approximate,  owing  to  the  great  difficulty  of  measuring 
high  temperatures  with  accuracy. 

While  it  is  difficult  to  establish  the  direct  relation  between 
the  temperature  of  a  body  and  the  light  emitted  by  it,  it  is 
comparatively  easy  to  determine  the  precise  relation  between 
the  light  emitted  and  the  factor  upon  which  the  temperature 
depends  —  the  heat-expenditure.  It  is  possible  to  measure 
accurately  both  the  heat  generated  in  an  incandescent  fila- 
ment per  second  (C2  B,  or  E  C),  and  the  candle-power,  and,  by 
doing  this  through  a  sufficient  range,  to  detect  the  law  of 
their  relation.  That  this  relation  should  be  a  general  one, 
and  not  simply  one  applicable  to  a  particular  case,  the  supply 
of  heat  must  be  expressed  in  terms  of  some  definite  standard. 
This  is  to  be  found  in  the  rate  of  the  generation  of  heat  per 
unit  surface.  We  can,  for  instance,  determine  the  amounts 
of  heat  which  must  be  generated  per  second  per  unit  of  sur- 
face to  give  one,  two,  three,  etc.,  candles  for  the  same  sur- 
face ;  or  we  can  assume  a  unit  rate  of  heat-generation  per  unit 
of  surface,  and  measure  the  candle-powers  corresponding  to 
any  number  of  such  units.  In  either  case  we  have  a  definite 
relation  between  the  heat-expenditure  and  the  light,  inde- 
pendent of  the  diameter  or  length  of  the  incandescent  body, 
provided,  of  course,  that  the  body  is  so  circumstanced  that  it 
loses  heat  only  by  radiation,  or  that  the  loss  by  other  means  is 
calculable. 

Though  we  have  no  experimental  determination  of  this  re- 
lation through  any  wide  range,  we  yet  have  some  data,  in  the 
results  obtained  in  the  measurement  of  incandescent  lamps, 
which  give  us  an  idea  of  its  character.  Eeferring  to  the 
measurements  of  the  Paris  committee  (page  185),  it  will  be 
seen  that,  to  double  the  light,  the  current  energy  (E  C)  was 
increased,  for  the  Maxim  and  Lane-Fox  lamps,  twenty-six  per 
cent ;  for  the  Edison,  twenty-eight  per  cent ;  and  for  the 
Swan,  thirty-seven  per  cent.  Taking  the  first  of  these  we  see 
that,  while  the  candle-powers  were  to  each  other  as  one  to  two, 
the  expenditures  of  energy  to  maintain  them  were  as  one  hun- 
dred to  one  hundred  and  twenty-six  ;  that  is,  the  candle-pow- 
ers were  to  each  other  as  the  cubes  of  the  current  energy.  As- 
suming this  relation  to  hold,  up  to  the  point  where  the  cur- 
rent energy  is  doubled,  we  should  have  the  candle-power  in 

14 


192  THE  INCANDESCENT  LIGHT. 

the  latter  case  eight  times  that  in  the  former,  or  would  get 
sixty -four  candles  instead  of  sixteen,  with  the  same  expendi- 
ture of  energy.  Since  the  two  measurements  were  those  of 
the  same  filament,  this  ratio  of  the  expenditures  of  energy  is, 
it  will  be  seen,  that  of  the  rates  of  the  generation  of  heat  per 
unit  of  surface.  It  can  hardly  be  supposed  that  the  rela- 
tion between  the  heat-expenditure  and  the  light  would  be  as 
simple  a  one  as  this,  through  a  wide  range  of  temperature. 
Doubling  the  energy  required  to  maintain  a  lamp  at  thirty- 
two  candles  would  probably  increase  the  light  more  than  eight 
times,  while  doubling  that  necessary  to  produce  one  candle 
would  show  a  much  less  gain  in  light.  The  real  relation  would 
be  a  varying  one — probably  one  in  which  the  light  would  in- 
crease slowly  at  first,  then  with  great  rapidity,  and,  finally, 
more  slowly  again. 

However  this  may  be,  the  important  point  to  be  noted  is 
that,  within  attainable  experimental  limits,  the  light  emitted 
by  an  incandescent  body  increases  very  rapidly  as  the  tem- 
perature is  raised,  and  that,  therefore,  economy  demands  the 
maintaining  the  filament  of  an  incandescent  lamp  at  the 
highest  possible  temperature.  The  practical  limit  to  the  tem- 
perature attainable  in  an  incandescent  filament  is  that  im- 
posed by  the  ability  of  the  filament  to  stand  the  strain  to 
which  it  is  then  subjected.  In  the  arc-lamp  the  incandes- 
cent material  is  constantly  renewed,  and  hence  it  may  be 
raised  to  a  much  higher  temperature  than  a  filament  whose 
continuity  must  be  preserved.  We  accordingly  get  much 
more  light  for  a  given  expenditure  of  current  energy  in  the 
former  than  in  the  latter  case.  If  it  were  possible  to  main- 
tain a  filament  at  the  same  temperature  as  the  carbon-points 
of  the  arc,  we  should  get  —  with  the  same  surface  exposed 
— not  only  as  good  but  a  superior  result,  as  the  filament 
would  be  free  from  loss  of  heat  by  exposure  to  the  air,  and 
there  would  be  a  smaller  loss  by  conduction.  We  are,  how- 
ever, very  far  from  this  condition  in  present  incandescent 
lamps,  and  can  not  hope  to  ever  reach  it,  though  we  may 
reasonably  expect  to  approach  it  much  more  nearly  than  has 
yet  been  done.  All  incandescent  lamps  are  run  at  compara- 
tively low  temperatures,  but  improvements  are  constantly 
being  made  in  the  filaments,  which  will  better  fit  them  for 
economical  working. 

Even  at  the  low  temperatures  at  which  it  is  at  present  run, 


EFFICIENCY   OF  THE  INCANDESCENT  LAMP.  193 

the  incandescent  lamp  is  still  a  vastly  more  efficient  instru- 
ment for  converting  heat  into  light  than  a  gas-flame.  Taking 
the  measurement  of  the  Edison  lamp,  made  by  the  Paris  com- 
mittee, we  find  the  expenditure  of  energy  in  maintaining  the 
filament  at  sixteen  candles  to  be  60 '16  watts,  or  '08  horse- 
power, and  the  expenditure  per  candle  3*76  watts.  To  arrive 
at  similar  figures  for  gas  it  is  only  necessary  to  calculate  the 
mechanical  equivalent  of  the  heat  produced  by  the  combus- 
tion of  the  requisite  amount  of  gas.  Ordinary  coal-gas  giving 
a  sixteen- candle  light,  with  a  consumption  of  five  feet  an 
hour,  may  be  taken  as  measuring  thirty-five  cubic  feet  to  the 
pound,  and  this  amount  as  evolving  by  its  combustion  12,500 
pound-degree  (centigrade)  units  of  heat.  Five  feet  will  there- 
fore evolve  1,785  such  units,  which  are  equal  to  810,000  calor- 
ies, since  the  centigrade  pound-degree  equals  453*6  gramme- 
degrees.  As  this  is  the  expenditure  per  hour,  that  per  second 
will  be  (810,000  -^  3,600)  225  calories,  equal  to  945  joules,  since 
one  calorie  equals  4 '2. joules.  As  a  joule  per  second  is  one 
watt,  we  have  energy  expended  in  a  five-foot  gas-flame  at  the 
rate  of  945  watts,  or  1  '26  horse-power.  The  expenditure  per 
candle  is  therefore  (945  -^  16)  59  watts,  as  against  3*76  in  the 
Edison  incandescent  lamp.  This  latter  is  consequently  over 
fifteen  times  more  efficient  than  a  gas-flame  as  a  light-pro- 
ducer. Even  allowing  this  amount  of  heat-energy  to  repre- 
sent twenty  candles  with  gas,  the  incandescent  lamp  is  still 
twelve  times  as  efficient. 

This  great  superiority  of  the  incandescent  lamp  has  hardly 
received  the  attention  it  deserves.  Comparison  has  usually 
been  made  between  it  and  the  arc-lamp,  and  its  comparative 
inefficiency  chiefly  dwelt  upon.  Yet  it  surpasses  gas  far  more 
in  this  respect  than  the  arc-lamp  does  it,  for,  by  the  tests  made 
at  Paris,  the  comparative  efficiency  of  these  two  is  as  one  to 
seven. 

The  considerations  presented  in  this  chapter  indicate  very 
clearly  the  direction  to  be  taken  by  efforts  to  improve  the  in- 
candescent lamp.  It  has  unquestionably  taken  its  final  form 
— that  of  a  strip  of  resisting  material  inclosed  in  an  exhaust- 
ed glass  envelope  —  a  form  of  such  extreme  simplicity  that 
nothing  more  remains  to  be  done  in  this  respect.  Attention 
must  hereafter  be  concentrated  upon  the  incandescing  strip 
itself,  as  on  its  improvement  depends  whatever  gain  in  econ- 
omy is  to  be  obtained.  Methods  of  constructing  this  incan- 


194  THE  INCANDESCENT  LIGHT. 

descent  portion  must  be  sought  for  which  will  give  it  increased 
ability  to  withstand  the  disintegrating  effects  of  high  tem- 
peratures, and  the  disrupting  action  of  the  current.  The  prob- 
lem is,  therefore,  but  partly  electrical ;  it  is  mainly  one  con- 
cerned with  a  consideration  of  the  structural  characteristics 
of  bodies  upon  which  their  power  of  withstanding  strains  of 
such  character  depends.] 


BOOK    IV. 
PKODUCTION   OF  ELECTRIC   CURRENTS. 


THE  production  of  electric  currents  by  chemical  action 
goes  back  to  the  discovery  of  Volta  in  1800,  and  it  is  the  form 
which  he  adopted  for  one  of  his  first  apparatus  that  gave 
them  the  name  of  Voltaic  Piles,  which  is  applied  to  all  those 
which  are  used  for  the  same  purpose.*  They  are  called 
hydro-electric  batteries  to  distinguish  them  from  thermo-elec- 
tric batteries,  in  which  currents  are  produced  by  the  direct  ac- 
tion of  heat  upon  two  metals.  The  first  batteries  used  were 
too  weak,  and  were  of  no  service  except  for  laboratory  ex- 
periments, which  were  very  costly.  Bunsen'  s  battery,  much 
more  powerful,  answered  in  some  exceptional  cases ;  but  it 
was  only  after  the  invention  of  the  machines  founded  on  the 
discoveries  of  Ampere,  of  Arago,  and  of  Faraday,  that  it  was 
possible  to  seriously  think  of  the  industrial  applications  of 
electricity,  especially  of  the  production  of  the  light  for  eco- 
nomic uses.  Since  that  time  the  hydro-electric  batteries  have 
been  almost  entirely  put  aside,  and  the  recent  progress  effect- 
ed in  the  transmission  of  electricity  will  soon  succeed  in  dis- 
couraging the  few  inventors  who  are  still  striving  and  now 
hoping  to  perfect  them.  We  have  little  need  of  occupying 
ourselves  with  them ;  but,  side  by  side  with  these  ordinary 
batteries  there  exist  others,  which  have  to  play  a  very  impor- 
tant part,  and  which  have,  moreover,  under  their  last  form, 
made  a  very  brilliant  entry  upon  the  industrial  stage  ;  these 
are  the  secondary  batteries,  invented  in  1859  by  M.  Plant e, 
and  proposed  to-day  to  serve  for  the  storage  and  transpor- 
tation of  electricity.  We  believe  it  will  be  useful  to  study 

*  This  is  true  only  in  FreDch.     In  English  the  name  battery  is  almost  univer- 
sally used  at  the  present  day. — TRANSLATOR. 


196  PRODUCTION  OF  ELECTRIC   CURRENTS. 

briefly  both  types  of  battery,  so  as  to  give  an  estimate  of 
the  resources  they  may  be  hoped  to  furnish. 

The  thermo-electric  batteries  are  so  much  the  more  inter- 
esting, as  they  represent  the  simplest  mode  of  producing  elec- 
tricity. Nothing  but  heat ;  no  machines,  no  complications  ;  a 
large  heater,  which  is  to  be  heated  regularly — this  is  the  solu- 
tion of  the  problem,  which  an  inventor,  M.  Clamond,  seemed 
to  have  nearly  attained  two  years  ago,  and  yet  no  model  of 
it  appeared  at  the  Electrical  Exhibition  of  Paris.  We  will 
study  this  apparatus,  because  we  are  in  hopes  that  it  will 
reappear  soon,  in  propria  persona,  or  another  of  the  same 
family,  which,  perhaps,  reserves  for  us  some  unexpected  sur- 
prise. 

We  will  examine,  finally,  the  machines  which  to-day  are 
our  principal  resource,  and  which  have  certainly  not  yet 
reached  their  limit. 


CHAPTER  I. 

HTDEO-ELECTRIC  BATTERIES. 

WE  have  seen  already  that  an  electric  current  can  only  be 
produced  when  the  equilibrium  of  the  molecules  is  disturbed 
by  some  particular  force,  called  electro-motive  force.  This 
force  can  be  obtained  by  chemical,  calorific,  or  mechanical 
.action.  It  is  also  probable  that  these  different  actions  are 
always  accompanied  by  electrical  manifestations,  but  it  is 
only  in  certain  particular  cases,  and  with  special  disposi- 
tions, that  it  is  possible  to  collect  this  electricity  in  utiliza- 
ble  form. 

The  chemical  action  is  effected  by  the  well-known  appa- 
ratus known  as  an  electric  battery,  an  apparatus  in  which  two 
substances  are  placed  in  each  other's  presence,  one  of  which 
is  attacked  by  the  other,  and  becomes  the  seat  of  an  electro- 
motive force. 

When  a  plate  of  pure  zinc  is  plunged  into  water  acidu- 
lated with  sulphuric  acid,  a  chemical  action  is  produced  :  the 
zinc  changes  its  state  ;  a  new  body  is  formed  by  its  combina- 
tion with  the  acid,  and  the  electric  molecules  which  were  in- 
closed in  the  metal  dart  through  the  water.  If  they  have  no 


HYDRO-ELECTRIC  BATTERIES.  197 

way  of  escape,  which  is  generally  the  case,  because  the  vessels 
employed  are  not  good  conductors,  they  accumulate  until  a 
new  equilibrium  is  produced,  and  the  electro-motive  force 
ceases  to  act.  But  if  there  is  placed  in  the  liquid,  by  the  side 
of  the  plate  of  zinc,  a  second  plate  formed  of  a  body  that  is  a 
conductor,  and,  be  it  understood,  unattackable  by  the  acid — a 
plate  of  carbon,  for  example — the  electric  molecules  will  accu- 
mulate there.  This  plate  will  then  be  charged  in  excess, 
while  the  plate  of  zinc  will  be  robbed  of  a  corresponding 
quantity  ;  the  accumulation  on  one  side,  and  the  impoverish- 
ment on  the  other,  will  attain  a  power  proportional  to  the 
energy  of  the  electro-motive  force  which  has  produced  them, 
and  which  maintains  them  without  going  any  further ;  but, 
as  soon  as  the  two  plates  shall  have  been  connected  one  with 
the  other  by  a  conducting  wire,  the  molecules  will  follow  the 
way  which  is  open  to  them,  and  will  rush  from  the  carbon 
plate  toward  the  zinc  plate,  where  they  will  receive  from  the 
electro-motive  force,  set  free,  a  new  impulse,  and  will  recom- 
mence the  same  round  as  long  as  this  force  will  suffice  to 
keep  up  their  movement.  The  electric  current  will  be  estab- 
lished. 

The  two  plates  are  called  electrodes.  The  plate  of  carbon 
represents  the  pole  of  accumulation,  or  positive  pole,  and  the 
plate  of  zinc  the  pole  of  rarefaction,  or  negative  pole.  In  the 
external  circuit  the  current  always  goes  toward  the  negative 
from  the  positive  pole,  while  in  the  interior  of  the  battery  it 
goes  from  the  zinc  to  the  carbon  plate.  The  first  one,  then,  is 
positive  with  respect  to  the  second  ;  it  follows,  and  it  is  some- 
thing which  must  not  be  forgotten,  that  the  negative  pole  of 
the  external  circuit  is  situated  on  the  positive  electrode,  and 
that  the  positive  pole  of  the  same  circuit  is  on  the  negative 
electrode. 

To  the  resistances  encountered  by  the  current  in  the  ex- 
ternal circuit  a  new  one  must  be  added — that  of  the  liquid 
—which  it  must  traverse  to  pass  through  the  space  which 
separates  the  two  plates ;  this  is  called  the  interior  resist- 
ance. The  two  resistances  must  be  added  together,  to  give  the 
total  resistance,  to  which,  as  we  have  seen,  a  corresponding 
tension  is  the  equivalent.  The  molecules,  which  have  acquired 
this  total  tension  under  the  influence  of  the  electro-motive 
force,  must  exhaust  a  part  of  it  in  overcoming  the  interior 
resistance ;  and  for  the  useful  work,  to  produce  which  the 


198  PRODUCTION  OF  ELECTRIC  CURRENTS. 

current  is  established,  to  be  as  great  as  possible,  this  first  ex- 
penditure should  be  equal  to  one  half  of  what  they  possess : 
in  effect,  if  they  expend  a  greater  quantity  in  the  first  circuit, 
they  will  not  have  enough  in  the  exterior  circuit ;  if  they 
expend  less,  they  will  have  an  excess  of  useless  tension,  and 
the  electro-motive  force  will  be  wasted.  From  this  it  will  be 
concluded  that  the  interior  and  exterior  resistances  should  be 
equal.  Now,  the  interior  resistance  has  a  definite  value,  im- 
posed by  the  nature  of  the  battery,  and  generally  insufficient 
to  fulfill  this  condition  ;  there  must  be  some  means  provided 
for  increasing  it,  and  for  this  it  is  enough  to  add  a  new  ele- 
ment by  the  side  of  the  first,  by  connecting  the  carbon  plate 
of  the  first  to  the  zinc  plate  of  the  second.  The  molecules 
coming  from  the  first  element  find  themselves  in  presence  of 
the  electro-motive  force  of  the  second,  which  will  give  a  new 
impulse  in  addition  to  that  which  they  have  already  received ; 
they  will  have  a  double  tension.  The  second  plate  of  carbon 
will  become  the  positive  pole  of  the  battery. 

It  will  be  seen  that  in  arranging  in  a  series,  one  after  the 
other,  the  necessary  number  of  elements,  a  sum  of  interior 
resistances  is  finally  reached  equal  to  the  exterior  resistance. 
This  is  called  connecting  a  battery  for  tension. 

If,  on  the  other  hand,  on  one  side  all  the  zincs  are  con- 
nected, and  on  the  other  side  all  the  carbons,  the  interior  re- 
sistance will  not  change,  because  it  will  be  the  same  at  each 
instant  in  all  the  elements.  What  happens  is  the  accumula- 
tion of  the  quantities  of  molecules  displaced  in  each  of  the 
elements,  and  a  consequent  increase  of  the  total  quantity. 
The  battery  is  connected  for  quantity. 

The  number  of  elements  necessary  to  obtain  a  current  of  a 
determinate  intensity  naturally  varies  with  the  nature  of  the 
substance  acting  in  it,  and  the  energy  of  the  resulting  chemi- 
cal action  ;  with  those  in  which  the  interior  resistance  is  con- 
siderable, the  chemical  action  is  more  prolonged ;  but  the 
electro-motive  force  can  only  displace  a  very  few  electrical 
molecules,  and  the  current  will  have  a  high  tension.  It  is 
often  impossible  to  use  them,  because  to  furnish  the  necessary 
quantity  of  electricity  the  current  would  attain  an  exaggerated 
tension. 

As  the  electro-motive  force  which  results  from  the  chemi- 
cal actions  is  usually  quite  feeble,  it  is  necessary  to  unite 
many  elements,  and,  when  it  is  necessary  to  have  a  current  of 


HYDRO-ELECTRIC  BATTERIES.  199 

considerable  intensity,  the  bulk  of  the  battery  becomes  very 
troublesome.  This  is  a  serious  inconvenience  ;  unfortunately, 
it  is  not  the  only  one. 

Chemically  pure  zinc  is  of  high  cost,  and  the  zinc  of  com- 
merce has  to  be  used.  This  contains  foreign  bodies  which 
permits  the  formation  in  the  electrode  of  a  number  of  small 
local  circuits ;  not  only  is  the  electricity  thus  disengaged 
lost,  but,  as  this  action  is  continuous,  even  when  the  exterior 
circuit  is  open,  the  zincs  are  consumed  without  producing 
any  useful  effect. 

To  remedy  this  evil  they  have  to  be  amalgamated — that  is 
to  say,  a  layer  of  mercury  has  to  be  spread  upon  their  sur- 
face which  combines  with  the  zinc  ;  thanks  to  this  species  of 
varnish,  the  chemical  action  only  exists  while  the  circuit  is 
closed,  and  the  zincs  are  preserved.  But  as  the  layer  of  amal- 
gam is  easily  detached  and  drops  to  the  bottom  of  the  cups, 
the  operation  has  to  be  repeated  whenever  the  battery  is  to 
be  used. 

The  chemical  action  does  more  than  attack  the  zinc  ;  at  the 
same  time  it  decomposes  the  water,  one  of  whose  constituent 
parts,  the.  oxygen,  combines  with  the  zinc,  but  whose  other 
part,  the  hydrogen,  remaining  free  in  the  liquid,  is  carried 
along  by  the  electrical  molecules  and  stops  on  the  surface  of 
the  carbon.  This  is  soon  covered  with  a  layer  of  gas,  a  very 
bad  conductor  ;  the  electric  molecules  can  not  pass  any  longer, 
and  the  electro-motive  force  ceases  to  act.  This  state  of  the 
carbon  plates  is  denoted  by  saying  that  it  is  polarized  /  we 
will  further  explain  this  expression. 

To  overcome  this  polarization,  the  constant  batteries  have 
been  invented,  in  which  is  placed  a  substance  capable  of  ab- 
sorbing the  hydrogen  as  fast  as  it  is  deposited  on  the  nega- 
tive electrode.  Becquerel  was  the  first  who  suggested,  in  the 
year  1829,  this  mode  of  effecting  this  end.  The  best  method 
consists  in  adding  to  the  liquid  a  metallic  salt  in  solution,  of 
the  same  nature  as  the  negative  electrode  ;  instead  of  gaseous 
hydrogen  the  battery  deposits  on  this  electrode  a  layer  of  the 
same  metal,  and  there  is  no  polarization.  This  is  the  arrange- 
ment adopted  by  Daniell  in  1836,  in  the  sulphate-of-copper 
battery  which  bears  his  name. 

To  prevent  these  two  liquids,  saturated  solution  of  sul- 
phate of  copper  and  acidulated  water,  from  mixing  too  rap- 
idly, the  first  is  inclosed  with  its  electrode  in  a  porous  cup, 


200 


PRODUCTION   OF  ELECTRIC   CURRENTS. 


FIG.  129.— Daniell  battery. 


through  which  it  slowly  passes,  and  keeps  the  passage  free 
for  the  electrical  molecules  (Fig.  129). 

In  1839  Grove  tried  nitric  acid,  very  rich  in  oxygen,  and 
easily  decomposed.  The  polarizing  hydrogen  combines  with 
part  of  the  oxygen  of  the  acid  ;  unfortunately,  this  last  is  thus 

decomposed  into  binoxide  of  nitrogen, 
and  this,  coming  in  contact  with  the 
air,  disengages  suffocating  fumes  of 
hyponitric  acid,  as  all  know  too  well 
who  have  worked  either  with  Grove's 
or  Bunsen's  battery,  which  only  differ 
in  the  substitution  of  gas-carbon  for 
platinum  as  negative  electrode  (Fig. 
131). 

There  are  many  other  combinations ; 
we  shall  only  recall  the  employment, 
as  depolarizer,  of  a  solution  of  bichro- 
mate of  potash  in  sulphuric  acid,  al- 
though this  system  of  battery,  invented  by  M.  Poggendorf, 
is  only  available  for  experiments  of  short  duration. 

Another  trouble  remains:  the  liquids,  whose  quantity  is 
limited,  change  their  composition  little  by  little ;  the  acidu- 
lated water  becomes  saturated  with  sulphate  of  zinc ;  the 
nitric  acid  is  replaced 
by  water ;  the  electro- 
motive force  progres- 
sively weakens,  and  in 
proportion  to  the  quan- 
tity of  electricity  sup- 
plied by  it.  The  con- 
stancy of  these  batter- 
ies, therefore,  is  only 
relative ;  it  never  ex- 
ceeds a  few  hours  when 
they  are  used  for  the 
electric  light.  If  they 
have  to  be  used  for  a 

longer  period  the  liquids  must  be  renewed,  and  that  so  as  not 
to  change  the  intensity  of  the  current.  To  overcome  these 
troubles  a  number  of  combinations  have  been  suggested,  of 
which  the  most  interesting,  from  the  point  of  view  of  our  stud- 
ies, we  shall  here  describe. 


FIG.  130. — Reynicr  battery. 


HYDRO-ELECTRIC  BATTERIES. 


201 


As  the  Daniell  battery  is  more  constant  than  the  Bunsen 
battery,  and  also  disengages  no  fumes,  M.  Carre  invented  in 
1868  an  arrangement  which  permitted  him  to  use  it  for  pro- 
ducing the  electric  light,  The  trouble  was  in  the  internal  re- 
sistance of  the  Daniell  battery  ;  to  diminish  this  resistance  M. 
Carre  gave  to  the  electrodes  a  very  large  surface,  and  replaced 
the  porcelain  cup  by  a  paper  vessel,  previously  treated  with 
sulphuric  acid,  called  parchment-paper. 

With  this  arrangement  five  Daniell  cups  could  be  substi- 
tuted for  three  Bunsen  cups,  and  a  battery  of  sixty  elements 
has  worked  for  two  hundred  successive  hours  without  weak- 
ening ;  it  sufficed  to  re- 
place every  twenty-four 
hours  by  pure 
water  a  part  of 
the  sulphate  of 
zinc  formed.  The 
light  obtained  cost  one 
franc  per  hour. 

Following  out  another 
order  of  ideas,  M.  Tom- 
masi  has  arranged  the 
Bunsen  pile  so  as  to  re- 
new constantly  the  acid- 
lated  water,  by  which  the 
action  is  kept  more  regu- 
lar, and  which  diminish- 
es a  little  the  work  of  de- 
polarization, because  the 
bubbles  of  hydrogen  are  in  part  carried  off  by  the  water. 
Besides,  the  porous  cups  are  enameled  over  their  lower  sur- 
face, which  serves  to  retain  the  necessary  quantity  of  nitric 
acid.  A  block  of  porcelain  causes,  by  displacement,  the  acid 
to  rise  into  the  upper  part  of  the  cup,  which  part  is  still 
porous.  Porcelain  stoppers  close  these  vessels  hermetically 
and  prevent  the  disengagement  of  hyponitric  acid ;  there  is 
some  fear  that  at  the  same  time  they  prevent  the  depolarization 
from  being  as  completely  effected  ;  it  appears  also  that  these 
batteries  have  a  little  more  electro-motive  force,  and  less  inte- 
rior resistance  than  the  Bunsen  battery  of  the  usual  model. 

A  more  important  modification  (Figs.  130  and  182)  has  been 
applied  by  M.  Eeynier  to  the  Daniell  battery,  to  increase  its 


FIG.  131. — Bunsen  battery. 


202 


PRODUCTION  OF  ELECTRIC  CURRENTS. 


electro-motive  force  and  diminish  its  interior  resistance.  The 
porous  cup  is  made  of  parchment-paper,  as  M.  Carre  had 
already  made  it ;  but  an  ingenious  way  of  folding  the  parch- 
ment made  the  execution  of  it  very  easy.  The  negative  elec- 
trode is  of  copper  and  the  depolarizing  liquid  is  a  solution 
of  sulphate  of  copper.  The  positive  electrode  is  always  of 
zinc,  which  need  not  be  amalgamated ;  but  the  acidulated 
water  is  replaced  by  caustic  soda.  The  natural  resistance  of 
these  two  liquids  is  diminished  by  the  addition  of  appropri- 
ate salts.  This  new  couple  is  more  energetic  than  the  other 
piles,  Bunsen  or  Daniell,  and  its 
interior  resistance  much  less.  It 
has  the  additional  advantage  of 
emitting  no  fumes,  and  the  invent- 
or hopes  to  succeed  in  regener- 
ating almost  completely  the  prod- 
ucts used  by  passing  through  the 
exhausted  solutions  a  quantity  of 
electricity  slightly  in  excess  of  that 
which  the  bat- 
tery has  emit- 
ted; the  cop- 
per deposited 
on  the  negative 
electrode  will 
be  dissolved, 
and  the  dis- 
solved zinc  reduced  to  the  metallic  state.  This,  then,  would 
constitute  a  fluid  for  the  storage  of  electricity. 

Other  inventors  have  sought  for  such  combinations  that 
the  battery  residues — that  is  to  say,  the  substances  produced 
after  the  electricity  had  been  developed  at  the  expense  of  the 
original  materials — would  have  a  value  in  commerce,  so  as  to 
diminish  the  cost  of  such  development ;  some  have  even  de- 
clared that  they  should  cost  nothing.  We  know  of  no  prac- 
tical result  due  to  these  researches,  without  doubt  perfectly 
justifiable,  but  which  are  so  complicated  by  the  commercial 
conditions  that  they  have  hitherto  been  fruitless. 

SECONDARY  OR  STORAGE  BATTERIES. 

This  name  is  given  to  batteries  in  which  two  substances  in 
presence  of  a  liquid,  after  having  been  subjected  to  a  first 


FIG.  132. — Small  model  of  the  circular  form  of  the  Eeynier  battery. 


HYDRO-ELECTRIC  BATTERIES.  203 

transformation  under  the  influence  of  the  passage  of  an  elec- 
tric current,  return  to  their  first  state,  disengaging  in  this 
second  transformation  a  certain  quantity  of  electricity.  The 
currents  thus  produced  are  called  secondary  currents.  It  is 
thus  that  in  an  ordinary  battery,  when  the  negative  electrode 
is  covered  with  hydrogen,  the  latter,  which  has  a  high  affinity 
for  oxygen,  tends  to  create  a  secondary  current  opposed  to 
the  principal  current.  The  negative  electrode  becomes  in  part 
positive  in  its  turn,  and  for  that  reason  is  said  to  be  polarized. 
Secondary  batteries,  properly  so  called,  are  those  in  which, 
instead  of  the  prevention  of  polarization,  its  development  is 
sought  after,  to  re-obtain  from  it  subsequently  the  work  it 
will  have  stored  up  ;  it  is  one  of  the  remarkable  applications 
of  the  reciprocity  or  reversibility  which  accompanies  the  pro- 
duction of  electricity.  Although  these  phenomena  were  first 
observed  by  Gautherot  in  1801,  it  was  only  in  1859  that  M. 
Plante  took  up  the  study  again  arid  invented  the  battery 
composed  of  plates  of  lead  so  well  known  to-day.  These  plates 
are  rolled  up  parallel  to  each  other  in  a  spiral,  and  are  sepa- 
rated by  bands  of  caoutchouc ;  they  thus  have  a  very  large 
surface  in  a  small  volume,  and  the  interior  resistance  is  low 
on  account  of  their  proximity.  They  are  contained  in  a  jar 
of  insulating  material,  ordinarily  of  glass,  and  this  jar  is  filled 
with  water  acidulated  with  one-tenth  part  of  sulphuric  acid. 
To  make  them  capable  of  storing  electricity,  it  is  necessary  to 
form  them,  by  causing  an  electric  current  from  an  external 
source  to  pass  a  number  of  times  through  the  cell,  first  in  one 
direction  then  in  the.  other.  At  each  passage  of  the  current 
the  oxygen  attacks  one  plate,  producing  on  it  a  coating  of  per- 
oxide of  lead ;  the  hydrogen  goes  to  the  other  plate  where  it 
escapes.  When  the  coating  of  peroxide  is  thick  enough,  the 
pile  is  formed,  and  then  it  is  necessary  to  be  careful  to  always 
charge  it  in  the  same  direction.*  Ordinarily  several  elements 
are  combined  by  means  of  a  switch,  which  admits  of  their 
being  connected  in  quantity  for  charging  and  in  tension  for 
discharging.  The  duration  of  this  discharge  is  proportional 
to  the  resistance  which  it  encounters.  Two  Bunsen  elements 
suffice  to  charge  twenty  secondary  elements,  and,  according  to 
M.  Plante,  the  return  is  equal  to  nine  tenths  of  the  electricity 

*  [The  object  of  the  "  forming  "  is  to  render  the  lead  plates  spongy  so  as  to 
get  as  large  a  surface  as  possible,  with  a  given  weight  of  material,  on  which  to 
deposit  the  active  oxide.] 


204  PRODUCTION   OF  ELECTRIC  CURRENTS. 

received.  The  current  can  be  preserved  for  a  long  time  ;  it  is 
nndiminished  at  the  end  of  eight  days,  and  can  fnrnish  cur- 
rents even  at  the  end  of  a  month. 

The  Plante  battery  had  received  already  numerous  appli- 
cations, when  quite  recently  M.  Faure,  impressed  with  the 
services  which  it  could  render,  and  perhaps  thinking  a  little 
of  those  which  it  might  render  him,  introduced  an  interesting 
modification.  To  make  the  coating  thicker  and  more  rapidly, 
he  covers  each  one  of  the  plates  with  minium  or  other  insolu- 
ble oxide  of  lead,  and  this  minium  is  retained  by  a  piece  of 
felt  riveted  on  the  plate  of  lead.  This  battery  is  formed, 
like  the  first,  by  passing  through  it  an  electric  current  which 
brings  the  minium  to  the  state  of  peroxide  on  the  positive 
electrode,  and  to  the  state  of  metallic  lead  on  the  negative 
electrode ;  when  it  is  discharged  the  reduced  lead  oxidizes, 
and  the  peroxide  is  reduced.  The  layers  within  which  these 
reactions  take  place  being  thicker,  the  storage  capacity  is  in- 
creased, but  to  an  amount  that  is  a  subject  of  dispute  :  the  in- 
ventor says  forty  times  ;  several  experimenters  say  one  and  a 
half  times.  It  is  probable  that,  in  attributing  to  the  Faure 
accumulator  a  power  three  times  that  of  the  Plante  battery, 
all  is  said  for  it  that  is  warranted. 

At  the  Electrical  Exposition  in  Paris  the  Faure  accumu- 
lators served  every  day,  for  five  or  six  hours,  to  supply  the 
incandescent  Swan  lamps,  which  lighted  -the  restaurant  in  the 
first  story  and  the  Judges'  Hall.  They  were  charged  during 
the  day,  in  three  or  four  hours,  with  currents  from  a  Siemens 
machine. 

We  have  nothing  to  say  in  reference  to  the  projects  for 
transporting  electricity  by  the  use  of  this  apparatus ;  it  is  a 
false  combination,  in  which,  among  other  fallacies,  it  does  not 
appear  how  the  purchaser  can  know  whether  the  battery 
which  is  brought  to  him  is  completely  charged,  and  whether 
that  which  is  removed  is  completely  exhausted.* 

Meanwhile,  although  somewhat  dear — one  hundred  and 
twenty-five  francs  for  an  element  of  eight  kilos,  representing 
one  kilogrammetre  for  eight  hours — these  batteries  can  be  of 
very  great  service,  and  it  is  easy  to  use  them  by  charging 
them  with  Thomson  batteries,  four  elements  for  a  secondary 

*  [Though  this  mode  of  supplying  storage  batteries  to  consumers  has  been 
suggested,  more  especially  at  the  time  of  revival  of  interest  in  them  several  years 
ago,  I  am  not  aware  of  its  having  been  seriously  advocated  by  any  one.] 


HYDRO-ELECTRIC  BATTERIES.  205 

Faure  element.  The  Thomson  battery  is  inodorous,  and  quite 
constant ;  it  can  work  day  and  night  without  any  interrup- 
tion, and  needs  no  other  care  than  the  addition  periodically 
of  some  crystals  of  sulphate  of  copper  and  replacement  by 
pure  water  of  a  part  of  the  solution  of  sulphate  of  zinc,  as 
it  becomes  saturated. 

They  might  even  now  be  employed  to  replace  the  six  or 
eight  Bunsen  elements,  which  have  found  a  last  asylum  on 
the  ground-floor  of  the  Opera,  and  which  repay  this  hospi- 
tality by  corroding  a  large  part  of  the  western  fagade. 

Before  M.  Faure,  Messrs.  Houston  and  Thomson  had  in- 
vented in  America  a  secondary  battery,  formed  of  two  plates 
of  copper,  immersed  in  a  solution  of  sulphate  of  zinc.  [The 
charging  current  is  sent  through  the  battery  from  the  upper 
to  the  lower  plate,  when  the  upper  plate  dissolves,  forming 
sulphate  of  copper,  which  floats  on  the  sulphate  of  zinc  ;  me- 
tallic zinc  is  deposited  upon  the  lower  plate.  The  battery 
when  charged  is  therefore  simply  a  gravity  Daniel.  M.  d'Ar- 
sonval  modified  this  by  using  for  one  electrode  lead  or  carbon 
covered  with  lead  shot,  and  for  the  other,  zinc.]  As  soon  as 
attention  was  directed  to  these  batteries,  new  ones  sprang  up 
on  all  sides,  such  as  those  of  MM.  d' Arson val,  Rousse,  Maiche, 
etc.  Evidently  secondary  batteries  are  destined  to  play  an 
important  role  in  the  distribution  of  electricity  as  regulators  : 
but  we  must  observe  that  the  name  of  accumulators  of  elec- 
tricity does  not  at  all  suit  them,  because  they  do  not  in  any 
sense  store  up  electric  currents.  That  which  they  do  store  up 
is  the  work  of  chemical  decomposition  between  certain  sub- 
stances whose  recombination  gives  back,  under  the  form  of 
an  electric  current,  a  part  of  this  work.  In  any  case  the 
attention  excited  by  them  in  these  latter  days  will  not  be 
useless ;  it  will  lead,  doubtless,  to  new  combinations  more 
powerful  and  more  advantageous. 

[Various  other  batteries  have  been  designed,  the  objects 
in  each  case  being  to  reduce  the  weight  of  the  material  as 
much  as  possible  in  relation  to  its  storing  power,  and  increase 
the  efficiency.  In  the  cell  of  M.  de  Meritens  the  lead  plates 
are  constructed  of  thin,  overlapping  laminae,  arranged  in  a 
manner  similar  to  the  slats  of  Venetian  blinds.  In  the  Sellon- 
Volckmar,  the  lead  plates  consist  of  a  lattice-work,  into  the 
open  spaces  of  which  the  red  oxide  is  forced,  this  construction 
giving  a  much  greater  amount  of  oxide  per  pound  of  lead 


206  PRODUCTION  OF  ELECTRIC  CURRENTS. 

than  when  this  is  on  the  surface  merely.  M.  de  Kabath  has 
obtained  increased  surface  by  the  use  of  corrugated  plates. 
A  number  of  patents  have  been  taken  out  by  Mr.  C.  F.  Brush, 
whose  arc-lamp  has  been  previously  described,  on  improved 
modes  of  constructing  the  plates  so  as  to  render  them  more 
durable  and  of  increased  storage  capacity.  Much  has  been 
claimed  for  this  battery,  but,  as  it  has  not  been  subjected  to 
tests  by  unbiased  experts,  nothing  is  known  of  its  perform- 
ance. A  form  of  battery,  claimed  by  its  inventor  to  be  supe- 
rior to  any  of  the  above,  has  been  designed  by  Mr.  Henry 
Button.  It  consists  of  a  positive  electrode  of  amalgamated 
lead  and  a  negative  one  of  copper,  immersed  in  a  solution  of 
sulphate  of  copper.  The  chemical  changes  in  this  cell,  when 
a  current  is  sent  through  it,  consist  in  the  combination  of  the 
oxygen  of  the  decomposed  solution  with  the  lead,  forming 
a  coating  of  the  insoluble  peroxide,  and  the  replacement  of 
the  copper  in  the  solution  by  the  disengaged  hydrogen,  the 
copper  being  deposited  on  the  negative  plate.  In  discharg- 
ing, the  copper  is  dissolved  in  the  solution,  and  the  lead  plate 
reduced,  the  cell  returning  to  its  original  chemical  condition. 

Many  tests  of  the  efficiency  of  the  storage-battery  have 
been  made,  but  the  results  of  different  experimenters  are  dis- 
cordant. Tests  of  the  Faure,  at  the  Conservatoire  des  Arts  et 
Metiers,  showed  that  this  accumulator  absorbed  forty  per 
cent  of  the  electrical  work  that  would  otherwise  have  been 
available  in  the  lamps  through  which  the  discharge  was  made. 
Sir  William  Thomson  placed  the  loss  at  twenty-five  per  cent, 
while  Professor  W.  E.  Ayrton  has  stated  that  it  need  not  ex- 
ceed eighteen  per  cent.  In  his  report  on  the  Sellon-Volckmar 
battery,  Professor  Henry  Morton  states  that  the  loss  does  not 
exceed  this  percentage  of  the  electrical  work  spent  in  charg- 
ing. He  found  that  one  cell,  weighing  eighty  pounds,  includ- 
ing that  of  the  box  and  liquid,  was  capable  of  yielding  a  cur- 
rent of  32*5  amperes  at  the  beginning,  and  31*2  amperes  at  the 
close  of  a  continuous  discharge  for  nine  hours.  The  electro- 
motive force  is  two  volts,  so  that  there  would  be  required  ten 
pounds  of  battery  per  Edison  sixteen -candle  lamp  for  each 
hour  of  burning ;  while  with  the  Faure  battery,  examined  at 
the  Paris  Conservatoire,  more  than  double  this  weight  would 
be  required. 

The  expectations  entertained  at  the  time  of  Faure's  im- 
provement, of  the  value  of  the  secondary  battery  in  the  in- 


THERMO-ELECTRIC   BATTERIES.  207 

dustrial  applications  of  electricity,  have  so  far  failed  of  realiza- 
tion. It  has  been  found  that  in  practical  operation  it  is  open 
to  many  objections.  The  first  cost  is  considerable,  it  greatly 
deteriorates  with  use,  and  its  efficiency  is  low.  Despite  the 
claims  which  have  been  made  for  the  various  batteries  as  they 
were  brought  to  public  attention,  the  battery  still  remains  a 
laboratory  apparatus,  in  which  much  improvement  must  be 
made  before  it  can  become  of  commercial  utility.  For  a  thor- 
oughly satisfactory  battery  there  is  doubtless  a  considerable 
field  of  usefulness,  but  its  value  in  electric  lighting  has  been 
greatly  overestimated.  The  feasibility  of  operating  incan- 
descent lamps  directly  from  the  dynamo  is  no  longer  doubtful, 
and  the  employment  of  the  storage-battery  in  an  extended 
distribution  presents  no  advantage,  while  it  is  certain  to  ma- 
terially enhance  the  cost  of  plant.] 


CHAPTER  II. 

THERMO-ELECTRIC  BATTERIES. 

IF,  after  having  soldered  together  by  one  of  their  extremi- 
ties two  bars  of  different  metals,  this  soldered  part  is  heated, 
the  difference  of  the  effects  produced  by  the  heat  in  each  one 
of  them  destroys  the  equilibrium  of  the  electric  molecules 
which  they  contain ;  and  when  the  two  free  extremities  are 
reunited  by  a  conductor,  a  current  is  produced,  going  from 
the  heated  part  to  the  cold  part,  in  that  one  of  the  two  metals 
which  is  the  best  conductor,  finally  traversing  the  whole  of 
the  exterior  circuit  and  returning  to  its  point  of  departure 
through  the  second  bar,  which  it  passes  through  in  opposite 
direction.  By  thus  soldering  in  a  series,  side  by  side,  a  num- 
ber of  bars  differing  alternately,  and  arranged  so  that  the 
solderings  of  the  even  row  can  be  heated  all  at  the  same  time, 
and  the  solderings  of  the  uneven  row  can  be  at  the  same  time 
cooled,  a  current  will  be  obtained  whose  strength  will  increase 
with  the  number  of  solderings  and  the  difference  of  their 
temperatures.  The  electro-motive  force,  due  to  these  effects, 
seems  above  all  to  depend  on  the  variations  in  electrical  con- 
ductivity, which  the  changes  of  temperature  produce  in  the 
metals  and  minerals  employed.  When  the  resistance  of  one 

15 


208  PRODUCTION  OF  ELECTRIC   CURRENTS. 

of  them  increases  with  the  heat  quicker  than  that  of  the 
other,  it  ends  by  producing  a  reversal  of  the  direction  of  the 
current.  This  is  what  actually  happens  with  iron-copper  and 
silver-zinc  couples. 

This  apparatus  is  the  thermo-electric  pile,  invented  ID  1821 
by  Seebeck.  For  a  long  time  it  was  only  an  excellent  labora- 
tory appliance,  under  the  form  given  it  by  Nobili.  In  1827 
the  elder  Becquerel,  to  whom  is  due  excellent  work  in  this 
branch,  had  constructed  one  with  artificial  sulphide  of  copper 
and  German-silver ;  it  was  composed  of  sixty  elements,  ar- 
ranged at  pleasure  in  one  single  or  two  parallel  series.  The 
solderings  were  heated  by  gas,  and  the  current  was  intense 
enough  to  redden  a  short  piece  of  fine  iron  wire. 

Toward  1870  M.  Clamond  took  up  again  the  study  of 
thermo-electric  piles,  and,  after  having  constructed  a  certain 
number  of  apparatus,  heated  by  gas,  which  gave  excellent  re- 
sults, he  attempted  the  construction  of  more  powerful  piles, 
designed  to  produce  the  electric  light.  He  seemed  to  have 
succeeded ;  for  we  have  seen,  in  1879,  a  pile  arranged  like  a 
radiator,  about  two  metres  high  and  one  metre  in  diameter, 
supply  two  lamps  with  Serrin  regulators  (Fig.  133) ;  each 
lamp  gave  a  light  of  about  thirty  carcels,  and  the  expense  was 
nine  to  ten  kilogrammes  of  coke  per  hour.  We  do  not  know 
why  these  piles  have  been  abandoned,  as  they  did  not  appear 
on  the  catalogue  of  the  Electrical  Exhibition  in  Paris  except 
as  a  laboratory  apparatus. 

M.  Clamond  used  iron  for  the  electro-positive  plates,  and 
for  the  others  an  alloy  composed  of  two  parts,  by  weight,  of 
antimony,  and  one  part  of  zinc.  Molds,  very  well  arranged, 
admitted  of  a  large  number  of  couples  being  made  at  one 
casting,  which  by  that  operation  were  joined  in  tension,  and 
formed  a  flexible  chain  easily  arranged.  These  chains  were 
compressed  between  two  frames,  termed  by  the  inventor  the 
collector  and  the  diffuser,  care  being  taken  to  isolate  them 
with  asbestus.  The  collector  was  composed  of  several  con- 
centric iron  cylinders  joined  together  by  ribs  running  length- 
wise, so  as  to  form  a  series  of  flues  between  the  cylinders  for 
the  circulation  of  the  warm  gases  from  the  source  of  heat ;  it 
also  acted  by  its  mass  as  a  regulator  of  the  temperature.  The 
diffuser  was  designed  to  facilitate  the  cooling,  and  for  that  pur- 
pose was  formed  of  plates  of  copper,  presenting  a  large  sur- 
face for  radiation.  Thus  the  difference  of  temperatures,  and 


THERMO-ELECTRIC   BATTERIES. 


209 


consequently  the  intensity  of  the  currents,  could  be  kept  con- 
stant. 

Thermo-electric  piles  are  simple,  economical,  and  easy  of 
application.  The  current  is  very  constant,  but  its  tension  is 
slight.  As  yet,  experiments  have  not  gone  far  enough  to  ad- 


FIG.  133.— Thermo-electric  pile  of  (Diamond. 

F,  fireplace,  with  ordinary  grate  for  coke. 
T  T,  central  cylindrical  chamber. 

0,  P,  collector,  consisting  of  two  annular  concentric  cylinders,  joined  by  ribs,  in  which  the 
heat  is  equally  diffused  by  its  movement  from  above  downward  in  the  space  O. 

C,  chain  of  thermo-electric  elements. 

D,  diffusers  of  heat. 

mit  of  our  estimating  the  action  of  the  heat  on  the  duration  of 
the  couples.  The  models  now  in  use  generally  experience  a 
considerable  increase  of  internal  resistance,  due  to  the  oxida- 
tion of  the  heated  solderings — an  oxidation  which  can,  never- 
theless, be  resisted  by  inclosing  them  in  a  metallic  capsule,  as 
in  the  thermo-electric  pile  of  Noe,  much  used  in  Austria. 


210  PRODUCTION   OF  ELECTRIC  CURRENTS. 

As  an  example  of  the  reversibility  of  electric  phenomena 
it  may  be  remarked  that  the  inverse  effect  of  the  thermo- 
electric pile  exists  in  Peltier's  experiment.  When  a  current 
passes  through  the  soldering  of  two  metals,  the  solder  is 
heated  or  cooled,  according  as  the  current  is  directed  in  the 
reverse  direction  or  in  the  same  direction  as  the  thermo- 
electric current  which  is  obtained  in  heating  this  same  sol- 
dering. 

Although  in  these  piles  the  heat  disengaged  by  combus- 
tion is  utilized  without  intermediary  apparatus,  it  is  but  in- 
completely used,  and  the  warm  gases  leave  the  apparatus  at 
a  considerable  temperature.  It  is  true  that  this  heat  can  be 
utilized  to  a  certain  extent  by  making  the  pile  serve  both  for 
heating  and  lighting. 

Many  have  thought  of  utilizing,  in  a  more  direct  fash- 
ion, the  combustion  of  carbon  by  collecting  the  electricity 
which  it  disengages.  In  the  year  1855  M.  Beequerel  ob- 
tained electric  currents  with  a  pile  in  which  the  carbon  in 
combustion  replaced  the  zinc  of  ordinary  batteries,  and  he 
called  the  currents  pyro-electric,  to  distinguish  them  from 
thermo-electric  currents.  This  is  how  he  himself  describes 
his  experiment :  "If  we  fasten  to  one  of  the  extremities  of 
the  wire  of  a  galvanometer  a  crucible  of  platinum  filled  with 
nitrate  or  chlorate  of  potash  in  fusion,  and  if  we  attach  to  the 
other  extremity  a  piece  of  retort-carbon  whose  end  has  first 
been  brought  to  a  red  heat,  then,  on  plunging  this  incandes- 
cent carbon  into  the  bath  in  fusion,  an  energetic  electric  cur- 
rent is  obtained  flowing  in  the  direction  that  would  make  the 
carbon  negative,  and  the  nitrate  of  potash  positive.  This 
effect  is  due  to  the  vivid  combustion  of  the  carbon  at  the  ex- 
pense of  the  oxygen  of  the  bath  of  fused  nitrate." 

For  the  experiment  to  succeed,  it  is  necessary  to  sustain 
the  piece  of  carbon  so  that  it  will  not  touch  the  walls  of  the 
crucible. 

In  1878  M.  Jablochkoff,  who  doubtless  feared  that  the 
complication  inseparable  from  machines  would  be  an  obsta- 
cle to  the  success  of  his  candles,  thought  also  of  collecting 
directly  the  electricity  which  is  disengaged  in  combustion ; 
probably  without  knowing  it  he  reproduced  the  experiment 
of  Beequerel.  He  melted  nitrate  of  soda  in  a  small  crucible 
of  cast-iron  ;  the  incandescent  carbon  dipped  into  this  bath  is 
burned  up  at  the  expense  of  the  oxygen  of  the  nitrate,  and 


ELECTRICAL  INDUCTION.  211 

plays  the  role  of  positive  electrode  ;  the  cast-iron  is  not  at- 
tacked, and  represents  the  conductor,  or  negative  electrode— 
that  is  to  say,  the  positive  pole  of  the  external  circuit. 

In  his  "  Treatise  on  the  Electric  Pile,"  M.  Maudet  judi- 
ciously remarks  the  curious  phenomenon  of  inversion  which 
this  experiment  presents.  If,  instead  of  nitrate  of  soda  in 
fusion,  this  nitrate  is  used  in  solution  in  water  at  the  ordi- 
nary temperature,  the  same  electrodes  play  opposite  roles ; 
the  iron  is  attacked  and  becomes  the  generator  electrode, 
while  the  carbon  will  be  the  conductor  electrode,  as  is  the 
case  in  all  the  batteries  where  we  have  seen  it  employed. 


CHAPTER  III. 

ELECTRICAL  INDUCTION. 

THE  production  of  electric  currents  by  machines  rests  upon 
a  number  of  discoveries,  which  we  shall  briefly  describe,  to 
make  the  mode  of  operation  of  these  machines  understood. 
In  July,  1820,  (Erstedt,  a  Banish  physicist,  observed  the  de- 
viation which  the  approach  of  a  magnet,  or  closed  circuit 
through  which  a  current  was  passing,  produced  upon  a  mag- 
netic needle.  The  analogy  between  magnetism  and  electricity 
was  then  established.  On  the  llth  of  September  next  fol- 
lowing, the  experiment  of  (Erstedt  was  repeated  before  the 
Academy  of  Sciences  by  M.  de  la  Rive,  and  some  days  after, 
on  the  20th  of  September,  Ampere  discovered  the  mutual 
action  which  two  currents  exercised  upon  each  other  ;  he  also 
proved  the  action  of  currents  upon  magnets  and  their  abso- 
lute reciprocity,  so  important  to  be  considered  in  all  the  appli- 
cations of  electricity.  On  the  25th  of  September  Arago  dis- 
covered that  currents  have  the  property  of  transforming  a  bar 
of  iron  or  steel  into  a  magnet ;  he  invented  the  electro-magnet 
at  the  same  time  that  Ampere  established  the  theory  of  mag- 
netism, basing  it  upon  the  analogous  properties  possessed  by 
magnets  and  solenoids.  Here  the  discoveries  of  reciprocity 
stopped  short,  and  it  was  only  ten  years  later,  in  1830,  that 
Faraday  discovered  induction — that  is  to  say,  the  property 
possessed  by  magnets  of  causing  electric  currents  to  arise  in 


212 


PRODUCTION  OF  ELECTRIC   CURRENTS. 


a  metallic  circuit.  It  is,  above  all,  to  the  use  made  of  this  last 
and  magnificent  discovery  that  electricity  owes  the  extraor- 
dinary progress  of  which  the  Electrical  Exhibition  in  Paris  in 
1881  furnished  us  such  varied  proofs. 

The  two  figures  annexed  illustrate  the  experiments,  to-day 
classic,  which  Faraday  performed,  both  with  a  magnet  and  a 
bobbin  of  copper  wire  traversed  by  a  current. 

When  there  is  plunged  into  a  bobbin  wound  with  a  long, 
fine  wire,  whose  coils  are  insulated,  a  second  smaller  bobbin, 
wound  with  a  short,  thick  wire,  and  traversed  by  a  current 
(Fig.  134),  there  is  instantly  produced  in  the  wire  of  the  first 
bobbin  an  energetic  current,  going  in  the  opposite  direction  to 
that  of  the  small  bobbin :  it  is  called  the  inverse  current;  this 
current  ceases  with  the  movement,  and,  as  long  as  the  small 
bobbin,  always  receiving  a  current,  remains  immovable  in  the 
large  one,  no  current  is  produced  ;  but,  at  the  moment  it  is 
withdrawn,  there  is  produced  in  the  wire  of  the  large  bobbin 
another  current,  this  time  in  the  same  direction  as  the  current 
of  the  small  one,  and  named  for  this  reason  the  direct  current. 


FIG.  134. — Experiment  of  Faraday  with  two  bobbins. 

The  current  of  the  small  bobbin  is  called  the  inducing 
current ;  those  which  are  produced  in  the  large  bobbin  are 
called  induced  currents,  or  currents  of  induction.  By  exten- 
sion these  qualities  are  often  applied  to  the  bobbins  them- 
selves. The  intensity  of  the  induced  current  increases  with 
the  intensity  of  the  inducing  one  and  with  the  rapidity  of  the 
movement ;  it  diminishes  at  the  same  time  with  these. 


ELECTRICAL  INDUCTION. 


213 


If,  instead  of  bringing  nearer  and  drawing  away  the  small 
bobbin,  it  is  held  motionless  within  the  large  one,  only  inter- 
rupting the  passage  of  the  current  through  it,  the  same  phe- 
nomena are  produced.  A  reverse  current  is  immediately 
started  in  the  wire  of  the  large  bobbin  at  the  moment  when 
the  inducing  current  is  started  in  the  wire  of  the  small  one  ; 
as  soon  as  the  current  is  established,  and  as  long  as  the  in- 


FIG.  135.— Experiment  of  Faraday  with  a  bobbin  and  magnet. 

ducing  current  continues  to  pass  through  the  wire,  it  will  pro- 
duce no  induced  current ;  but  at  the  moment  when  the  in- 
ducing current  is  stopped,  a  direct  current  will  manifest  itself 
in  the  large  bobbin.  We  will  see  below  how  each  of  these 
two  modes  of  induction  has  been  utilized. 

The  same  phenomena  are  produced  when  the  small  bobbin 
is  replaced  by  a  magnetized  bar  (Fig.  135),  either  when  the 
bar  is  displaced  under  the  same  conditions,  or  when  its  mag- 
netization is  made  to  vary  by  the  approach  or  removal  of  a 
second  magnet. 

The  phenomena  of  induction,  as  well  as  those  of  electrical 
attraction  and  repulsion,  show  clearly  that  the  influence  of 
a  body  charged  with  electricity  or  magnetism  extends  to  a 
considerable  distance  around  it.  For  magnets  and  electro- 
magnets the  space  within  which  this  influence  can  be  per- 
ceived is  called  the  magnetic  field;  by  analogy,  the  space 
under  the  influence  of  a  current  is  called  the  galvanic 
field. 


214  PRODUCTION  OF  ELECTRIC  CURRENTS. 

We  can  not  here  enter  upon  the  consideration  of  the  hy- 
potheses by  whose  aid  the  action  of  this  influence  is  explained. 
The  theory  of  particular  fluids,  generally  accepted  formerly, 
is  to-day  abandoned,  and  it  is  rather  believed  that  electric 
and  magnetic  action  is  due  to  vibrations  or  movements  in  the 
layers  of  ether  which  exist  in  all  bodies,  and  by  which  they 
are  surrounded. 

If  the  cause  is  unknown,  the  effects  can  be  represented 
materially  by  the  aid  of  those  curious  figures  which  M.  de 
Haldat  has  named  magnetic  phantoms,  and  which  are  ob- 
tained with  very  fine  iron  filings  spread  upon  a  piece  of  paper 
or  glass  placed  above  the  poles  of  a  magnet.  The  magnetic 
force  orientates  these  filings  in  a  series  of  lines  converging 
from  one  pole  to  the  other,  and  which  repel  each  other  when 
two  poles  of  the  same  name  are  brought  together.  These 
lines,  which  Faraday  has  named  lines  of  magnetic  force,  are 
very  convenient  to  illustrate  the  effects  of  induction  which 
accompany  the  movement  of  a  conducting  wire  through  a 
magnetic  field. . 

Each  of  the  lines  of  force  which  the  wire  intersects  in  pass- 
ing starts  an  induced  current,  and  the  quantity  of  electricity 
developed  is  proportional  to  the  number  of  lines  intersected 
in  a  given  time.  The  direction  of  the  movement  in  relation  to 
the  direction  of  the  lines  of  force  determines  that  of  the  cur- 
rents. It  is  equally  apparent,  on  inspection  of  these  magnetic 
phantoms,  that  the  density  of  the  lines  of  force  diminishes  in 
proportion  as  they  are  removed  from  the  poles,  and  it  is  thus 
manifest  why  it  is  so  important  for  the  wire  to  move  in  the 
densest  regions — that  is  to  say,  the  nearest  possible  to  the  in- 
ductors. The  farther  it  is  removed,  the  more  will  it  be  neces- 
sary to  augment  the  velocity  of  displacement,  to  obtain  again 
the  same  intensity  of  induced  current. 


RUHMKORFF'S  COIL. 

We  have  seen  that  induction  can  exert  itself  in  two  ways  : 
1.  The  inducing  and  induced  current  circuits  are  immova- 
ble ;  the  induced  currents  are  produced,  either  by  variations 
in  the  intensity  of  the  inducing  current,  or  by  variations  in 
the  magnetism  of  the  magnet. 

2.  The  intensity  of  the  inducing  current  and  the  magnet- 
ism of  the  magnet  are  invariable ;  the  induced  currents  are 


ELECTRICAL  INDUCTION.  215 

produced  by  the  relative  displacement  of  the  inducing  or  in- 
duced circuit. 

The  first  of  these  two  modes  of  induction  was  employed 
in  1842  by  MM.  Masson  and  Breguet  in  the  construction  of 
the  induction-coil  named  after  Ruhmkorff,  in  memory  of  the 
ingenious  constructor  who  gave  it  such  high  power.  This  coil 
is  formed  of  two  copper  wires,  perfectly  insulated,  wound  into 
coils,  one  on  top  of  or  beside  the  other.  One  wire,  short  and 
thick,  conducts  the  inducing  current,  to  which  a  small  special 
apparatus  communicates  a  series  of  interruptions.  From  this 
a  succession  of  inverse  and  direct  induced  currents  results, 
whose  intensity  is  proportional  to  the  square  of  the  resistance 
of  the  wire  of  the  induced  circuit,  to  the  intensity  of  the  in- 
ducing current,  and  to  the  rapidity  of  the  interruptions.  Be- 
sides this,  the  coil  contains  a  bundle  of  pieces  of  iron  wire, 
whose  successive  magnetizations  and  demagnetizations,  due 
to  the  interruptions  of  the  inducing  current,  increase  to  a  con- 
siderable extent  the  intensity  of  the  induced  currents.  Fig. 
136  represents  one  of  the  models  adopted  for  demonstrations 
in  courses  of  physics. 

The  quantities  of  electricity  put  in  motion  in  each  induced 
current  are  equal ;  but  the  direct  current  has  a  higher  tension. 
This  follows  from  the  variations  in  the  inducing  current  due 
to  the  induction  it  exercises  upon  itself  in  its  own  circuit. 
This  induction  of  an  intermittent  current  upon  itself  is  very 
important ;  it  is  exercised  every  time  a  circuit  is  formed  by  a 
coiled  wire,  whose  spires  approach  each  other,  and  causes  the 
production  in  the  same  wire  of  induced  currents,  called  extra 
currents. 

When  the  circuit  is  opened  an  extra  current  is  produced, 
which,  following  the  general  law  of  induction,  is  inverse — that 
is  to  say,  the  reverse  of  the  principal  current,  whose  intensity 
it  diminishes.  When  the  circuit  is  closed,  the  extra  current 
is  direct,  and  adds  itself  to  the  principal  current,  whose  in- 
tensity it  increases  and  whose  duration  it  prolongs.  It  in- 
creases the  power  of  the  spark  at  breaking,  but  at  the  same 
time  it  prolongs  the  duration  and  weakens  the  tension  of  the 
corresponding  induced  current. 

To  overcome  the  effects  of  these  extra  currents,  M.  Fizeau 
interposes  in  the  inducing  circuit  a  condenser  of  large  surface, 
in  which  the  electricity  of  the  extra  current  accumulates,  to 
subsequently  react  again  in  the  opposite  direction. 


216 


PRODUCTION  OF  ELECTRIC,  CURRENTS. 


The  Ruhmkorff  coil  produces  very  powerful  calorific  ef- 
fects ;  it  has  had  some  practical  applications  in  the  ignition 
of  mines  and  illumination  by  means  of  Geissler  tubes.  An 
attempt  has  also  been  made  to  utilize  it  for  lighting  by  means 
of  incandescence,  and  we  must  recall  the  curious  experiments 
made  by  M.  Jablochkoff  in  1877  with  a  thin  plate  of  kaolin 
placed  between  the  extremities  of  the  secondary  wire  of  one 
of  these  coils.  The  surface  of  this  plate  was  kept  in  fusion 
by  the  passage  of  the  currents,  and  gave  a  very  beautiful 


FIG.  136.— Ruhmkorff  coil. 
B,  coil. 

P,  P',  connecting  wires  of  the  inducing  current. 

i,  reversing  commutator  of  M.  Bertin,  permitting  of  controlling  the  current. 
i,  i',  terminals  of  the  induced  circuit, 
a,  a,  a,  a',  inducing  current  circuit  wires. 

S,  base  containing  the  condenser,  kept  in  a  movable  drawer  which  may  be  drawn  out,  accord- 
ing to  the  current  required,  by  unscrewing  the  screws  0,  o  and  pulling  it  out  a  little. 
M,  bundle  of  iron  wire. 
E,  E',  vibrating  commutator  or  interrupter. 

light.  By  varying  the  dispositions  and  sizes  of  the  coils,  as 
well  as  the  number  of  plates  ignited  by  each  of  them,  lights 
of  different  intensities  can  be  obtained,  from  a  half-carcel  up 
to  two  carcels.  M.  Jablochkoff  supplied  his  induction-coils 
from  a  machine  with  alternating  currents,  so  that  he  could 
suppress  in  each  of  them  the  condenser  and  interrupter,  and 
consequently  increase  considerably  the  intensity  of  the  in- 
duced currents. 

Analogous  trials  have  been  recently  made  in  England,  fol- 
lowing out  the  experiments  made  by  Mr.  Spottiswoode,  with 


THEORETICAL  PRINCIPLES   OF 

an  induction-coil  excited  by  alternating  currents  from  a  ma- 
chine of  M.  de  Meritens.  These  trials  apply,  above  all,  to 
processes  of  incandescence  which  require  a  current  of  con- 
siderable tension,  a  tension  which  can  hardly  be  derived  di- 
rectly from  the  machine.  The  Ruhmkorff  coil  is  really  an 
apparatus  for  transformation  ; :  though  it  ordinarily  is  only  em- 
ployed to  transform  dynamic  into  static  electricity,  it  can 
also  effect  the  opposite  transformation,  as  M.  Bichat  has 
shown,  in  passing  into  the  fine  wire  of  the  coil  a  series  of 
sparks  which  caused  in  the  large  wire  alternate  induced  cur- 
rents, producing  effects  analogous  to  those  of  battery-currents. 

The  induction-coil  with  which  Mr.  Spottiswoode  made  his 
experiments  is  the  largest  that  has  ever  been  constructed.  Its 
total  weight  is  762  kilogrammes,  its  length  1  '22  metres,  and  its 
external  diameter  '508  metre.  The  primary  wire  is  2£  milli- 
metres in  diameter,  and  445  metres  long.  The  secondary  coil 
is  wound  with  no  less  than  458  kilometres  of  fine  wire,  mak- 
ing 341,850  turns,  divided  into  several  bobbins  in  juxtaposi- 
tion, according  to  the  system  of  M.  Poggendorff. 

With  30  quart  cells  of  Grove's  battery,  it  gives  sparks  1'08 
metres  (42J-  inches)  in  length.  With  currents  from  the  Meri- 
tens machine,  the  spark  forms  a  true  voltaic  arc  of  15  to  20 
centimetres'  length. 


CHAPTER  IV. 

THEORETICAL  PRINCIPLES   OF  MACHINES. 

THE  second  mode  of  induction — that  which  results  from 
the  relative  displacement  of  the  inducing  or  induced  circuit- 
has  been  much  more  fertile  of  application ;  upon  it  depend 
the  construction  and  working  of  machines  destined  for  the 
production  of  dynamic  electricity.  Although  presenting  a 
great  variety  of  forms,  these  machines  all  contain  the  same 
two  elements — the  inducing  and  induced  circuits — repeated  a 
sufficient  number  of  times  ;  one  of  the  two,  generally  the  in- 
duced circuit,  has  imparted  to  it  a  very  rapid  movement  of 
rotation  in  the  magnetic  field  of  the  inductor,  and  it  is  the 
mechanical  work  expended  in  moving  it  that  is  transformed 
into  electricity. 


218  PRODUCTION  OF  ELECTRIC   CURRENTS. 

The  former  frictional  machines  also  transformed  mechani- 
cal work  ;  but  they  only  served  to  multiply  charges  of  static 
electricity — that  is  to  say,  to  raise  the  potential  at  the  two 
ends  of  an  open  circuit,  and  not  to  maintain  a  continual  flow 
of  dynamic  electricity  in  a  closed  circuit. 
I  At  first  the  inductors  were  composed  of  permanent  mag- 
nets ;  as  the  power  of  these  magnets  is  limited,  and  as  their 
weight  and  dimensions  increase  in  greater  proportion  than  the 
power,  to  increase  the  power  of  these  machines,  electro-mag- 
nets were  employed  in  which  an  electric  current  develops  an 
enormously  greater  amount  of  magnetism  than  a  permanent 
magnet  of  the  same  dimensions  could  contain.  According 
to  this  difference  in  the  inductors,  the  machines  are  ranged 
in  two  categories :  magneto-electric  machines,  in  which  the 
inductors  are  permanent  magnets ;  and  dynamo-electric,  in 
which  electro-magnets  are  the  inductors. 

This  classification,  which  is  sanctioned  by  usage,  is  inexact, 
because  magnetism  and  motion  play  the  same  role  in  both 
classes,  and  because  there  is  no  magneto-electric  machine 
which  may  not  become  dynamo-electric  by  the  simple  change 
of  inductors,  and  vice  versa. 

In  the  first  machines  of  the  dynamo-electric  type,  the  cur- 
rent necessary  to  produce  and  sustain  the  magnetism  of  the 
inductors  was  furnished  by  a  small  auxiliary  magneto-electric 
machine.  This  was  the  first  application  of  exciting-machines. 
The  system  was  soon  simplified  by  the  use  of  two  separate 
circuits,  the  current  in  one  of  which  excited  the  field  mag- 
nets, while  that  in  the  other  performed  the  external  work. 
Eventually  a  third  arrangement,  yet  more  simple,  was  reached : 
the  entire  production  of  the  machine  was  reduced  to  a  single 
current,  which  was  made  to  pass  in  its  entirety  through  the 
field  coils  before  passing  into  the  external  circuit ;  this  last 
arrangement,  generally  adopted  at  the  present  day,  gives  us 
without  complication  the  maximum  magnetic  power  and  the 
maximum  intensity  of  current  that  can  be  derived  from  the 
organs  of  a  machine  of  given  dimensions ;  it  has,  however, 
the  inconvenience  of  making  the  work  of  the  machine  in- 
versely proportional  to  the  variations  in  external  resistance  ; 
if  this  increases,  the  intensity  of  the  current  diminishes, 
which  weakens  the  inducing  magnets,  while,  as  a  rule,  the 
reverse  is  necessary.  When  the  external  resistance  dimin- 
ishes, the  intensity  of  the  current  and  power  of  the  inducing 


220 


PRODUCTION  OF   ELECTRIC  CURRENTS. 


magnets  increases  ;  from  this  results  a  useless  expenditure  of 
work-,  and  often  a  production  of  heat  dangerous  to  the  struct- 
ure of  the  machine.  To  overcome  this  trouble  it  suffices  to 
send  around  the  magnets  a  current  shunted  from  the  principal 
one,  reducing,  of  course,  the  thickness  of  the  wire  with  which 
they  are  wound.  The  relation  is  then  reversed.  If  the  ex- 
ternal resistance  increases,  the  derived  current  increases  also, 
and,  along  with  it,  the  excitation  of  the  inducing  magnets 
and  intensity  of  the  current  produced.  If  this  exterior  re- 
sistance diminishes,  the  derived  current  also  grows  weaker, 
and  the  work  absorbed  is  reduced  in  proportion.  It  only  re- 
mains necessary  to  see  that  the  machine  does  not  work  with 
an  open  outer  circuit ;  for  then  the  shunt  circuit  would  alone 
remain  closed,  and  work  would  be  uselessly  expended. 


FIG.  138.— Magneto-electric  machine. 


FIG.  139.— Separately  excited  dynamo. 


[The  four  ways  in  which  the  magnetism  of  the  field  of  a 
machine  may  be  maintained  are  shown  in  Figs.  138, 139,  140, 
and  141.*  The  magneto  machine,  with  a  field  formed  of  per- 
manent magnets,  is  shown  in  Fig.  138,  and  the  dynamo,  with 

*  From  the  journal  of  the  Society  of  Arts. 


THEORETICAL  PRINCIPLES  OF  MACHINES. 


221 


its  field  magnets  excited  from  an  external  source,  in  Fig.  139. 
It  will  be  seen  that  in  both  of  these  cases  the  magnetization 
of  the  field  is  independent  of  the  current  flowing  through  the 
working  circuit,  which  is  not  the  case  in  the  two  remaining 
forms,  in  which  a  whole  or  part  of  the  current  generated  by 


Fia.  140. — Series  dynamo. 


FIG.  141. — Shunt  dynamo. 


the  machine  is  used  to  excite  the  field  magnets.  The  type 
of  dynamo  in  which  the  whole  current  of  the  machine  passes 
through  the  field-magnet  coils  is  represented  in  Fig.  140.  It  is 
known  as  the  "  series  dynamo,"  and  until  recently  was  almost 
exclusively  employed  in  arc-lighting.  The  dynamo  in  which 
but  a  portion  of  the  current  is  used  to  energize  the  field-  mag- 
nets, termed  the  "  shunt  dynamo,"  is  shown  in  Fig.  141. 
Evidently  in  both  of  these  types  of  machine  the  strength 
of  the  magnetic  field  will  depend  upon  the  resistance  in  the 
working  circuit,  since  the  magnetization  depends  upon  the 
strength  of  the  current  circulating  in  the  field  coils.  Various 
methods  have  been  devised  for  keeping  the  strength  of  the 
magnetic  field  in  the  proper  relation  to  the  external  circuit, 
which  will  be  found  described  in  Book  V. 


222  PKODUCTIQN   OF  ELECTRIC   CURRENTS. 

The  two  different  methods  of  arranging  electric  lamps  upon 
a  circuit,  "in  series"  or  "in  multiple  arc,"  often  spoken  of  as 
"in  derivation,"  are  also  shown  in  Figs.  140  and  141.  In  the 
series  method,  used  exclusively  with  arc-lamps  and  with  open- 
air  incandescent  lamps,  the  lamps  are  strung  one  after  another 
upon  the  same  circuit.  This  is  shown  in  Fig.  140.  When 
placed  in  multiple  arc,  the  method  always  adopted  with  in- 
candescent lamps,  the  lamps  are  placed  across  the  circuit,  as 
shown  in  Fig.  141,  so  that  one  terminal  is  connected  with  the 
outgoing  and  the  other  with  the  return  wire.  In  the  series  sys- 
tem the  strength  of  the  current  is  evidently  the  same,  what- 
ever the  number  of  lamps,  but  the  electro-motive  must  vary 
with  them.  In  the  multiple-arc  system,  on  the  contrary,  the 
electro-motive  force  should  remain  constant,  and  the  strength 
of  the  current  be  in  proportion  to  the  number  of  lamps.] 

We  see  now  that  in  this  disposition  of  parts  the  inducing 
electro-magnets  are  excited  by  the  passage  of  currents  which 
they  themselves  induce.  As  the  magnetization  of  the  iron  by 
these  currents  is  only  temporary,  the  magnetism  of  the  in- 
ducing magnets  disappears  as  soon  as  the  machine  stops, 
and  the  question  arises  as  to  what  produces  the  induction 
when  the  machine  is  started  again.  This  induction  is  simply 
produced  by  the  traces  of  magnetism,  extremely  feeble,  it  is 
true,  which  the  iron,  soft  as  it  may  be,  is  certain  to  preserve 
after  it  has  been  once  magnetized,  and  which  is  called  residual 
magnetism.  It  is  this  residual  magnetism,  which  is  so  hard 
to  avoid  in  telegraphic  apparatus,  that  becomes  a  most  valu- 
able auxiliary  for  charging  the  machine. 

When  the  machine  starts,  this  trace  of  magnetism  starts  at 
once  an  imperceptible  induced  current ;  this  current  passing 
into  the  coils  of  the  inducing  magnets  increases  a  little  their 
magnetism ;  at  the  second  turn  the  current  is  a  little  stronger, 
and  the  magnetism  increases  a  little  more  ;  the  power  of  the 
inducing  magnets  thus  successively  increases  until  they  are 
saturated.  Residual  magnetism  generally  exists  even  in  new 
machines,  and  is  attributed  either  to  the  operations  which 
the  inducing  magnets  go  through  in  the  process  of  construc- 
tion, or  to  the  influence  of  terrestrial  magnetism.  It  is  rarely 
necessary  to  charge  a  machine  before  starting  it,  and,  at  the 
most,  a  short  application  of  a  battery-current  suffices. 

The  armature  coils  are  generally  wound  with  a  wire  or  rib- 
bon of  copper,  whose  length  and  section  are  determined  by 


THEORETICAL  PRINCIPLES  OF  MACHINES.  223 

the  tension  which  the  current  is  to  possess.  The  strength  of 
the  field  and  the  speed  being  constant,  the  tension  of  the  in- 
duced currents  increases  with  the  resistance  of  the  wire,  but 
only  of  that  part  of  the  wire  that  is  active  and  contributes  to 
the  production  of  the  currents  ;  the  resistance  of  the  inactive 
portion,  although  inevitable,  has  nothing  to  do  with  the  ten- 
sion to  be  finally  produced.  *  We  must  further  observe  that  the 
co-efficient  of  resistance  of  copper  is  not  the  only  factor  to  be 
taken  into  account,  because  the  winding  of  the  wire  causes 
the  wires  that  are  close  together  to  react  upon  each  other,  in 
proportion  to  the  intensity  of  the  currents  that  successively 
traverse  them  ;  it  follows  that  the  real  resistance  of  a  coil  is 
much  greater  than  the  theoretical  resistance  calculated  for 
the  same  length  of  uncoiled  copper  wire.  Thus  it  appears 
that  it  is  possible  with  the  same  parts,  by  the  mere  difference 
of  dimensions  of  the  armature  coil,  to  produce  from  machines 
currents  of  tension  or  of  quantity. 

The  copper  used  should  be  as  pure  as  possible,  because 
its  conductivity  is  rapidly  diminished  by  the  presence  of 
foreign  bodies ;  iron  being  a  much  inferior  conductor,  more 
of  it  must  be  employed,  and  the  weight  of  the  moving  parts 
of  the  machine  increased  ;  it  also  is  susceptible  of  magnetiza- 
tion, and  the  mass  of  metal,  formed  by  the  coils  of  iron  wire, 
would  react  upon  the  cores  and  weaken  their  magnetism. 

The  armature  coils  are  generally  wound  in  the  form  of 
helices  or  bobbins,  upon  one  or  more  soft-iron  cores  which 
support  them.  The  alternations  of  magnetization  and  demag- 
netization which  these  cores  experience  on  account  of  their 
movements  in  front  of  the  inducing  magnets,  give  a  new 
electro-motive  force,  which  further  increases  the  charge  of 
magnetism  produced  by  each  formation  of  current  in  the 
helices.  Unfortunately,  the  influence  of  the  inductors  is 
not  limited  to  modifying  the  magnetic  state  of  the  cores ; 
it  causes  at  the  same  time  the  production  of  induced  cur- 
rents which  bring  about  the  production  of  heat  and  increased 

*  [Resistance  in  any  part  of  the  circuit  does  not  contribute  to  the  tension  of 
the  induced  current.  This  depends  upon  the  number  of  lines  of  force  cut  per 
second  by  the  rotating  conductor.  The  total  electro-motive  force  generated  will 
be  the  sum  of  those  set  up  in  each  turn  of  wire ;  hence,  for  the  production  of 
currents  of  high  tension,  many  turns  of  wire  are  necessary,  which  increases  the 
resistance.  In  order  to  bring  all  parts  of  the  coil  within  the  inductive  influence 
of  the  field,  finer  wire  must  be  used,  further  increasing  the  resistance.] 
16 


224 


PRODUCTION  OF  ELECTRIC  CURRENTS. 


resistance  to  movement.  Faraday  proved  the  existence  of 
these  currents  by  reversing  the  experiment  of  Barlow's  wheel. 
The  apparatus  of  Faraday  (Fig.  142)  suffices,  on  the  other 
hand,  to  demonstrate  the  two  inverse  actions  of  magnets 
on  currents,  and  the  induction  produced  by  these  currents. 
Faraday's  apparatus  was  the  first  machine  and  the  first  mag- 
neto-electric motor.  The  parasitical  currents  of  electricity 
are  often  called  Foucault  currents,  because  it  is  to  this  phys- 
icist that  the  apparatus  is  due  which  serves  to  demonstrate 
the  transformation  into  heat  of  the  work  which  they  repre- 
sent. To  reduce  as  far  as  possible  the  formation  of  these 

A,  inducing  magnet. 
D,  induced  disk. 

B,  binding-screw  for  entry  or 
exit  of  currents  by  the  axis 
of  the  disk. 

B',  binding- screw  connecting 
with  a  rubber  w,  for  en- 
trance or  exit  of  currents 
by  the  exterior  circumfer- 
ence of  the  disk. 

If  the  galvanometer  is 
placed  between  the  termi- 
nals at  B,  B',  and  the  disk 
is  turned  by  hand,  the  ex- 
istence of  a  continuous  cur- 
rent will  be  shown,  whose 
direction  depends  on  the 
direction  of  the  rotation  of 
the  disk. 


FIG.  142. — Faraday's  apparatus. 


If  the  galvanometer  is  replaced  by  a  Bunsen  cell,  its  terminals  being  connected  to  the 
binding-screws  B,  B',  the  disk  begins  to  turn,  and  the  direction  of  rotation  depends  on 
the  direction  of  the  current  passing  through  the  disk.  To  show  the  transformation  into 
heat,  a  very  powerful  magnet  is  needed,  and  a  very  rapid  rotation  of  the  disk.  (Fou- 
cault' s  and  M.  Le  Eoux's  apparatus). 

currents,  the  cores  are  constructed  of  sheet-iron  or  of  iron 
wire  ;  in  some  recent  machines  they  are  entirely  suppressed  ; 
in  these  the  bobbins  are  supported  by  standards  of  wood  or 
other  non-magnetic  and  non-conducting  material. 

The  wires  used  in  the  machines  should  be  .more  perfectly 
insulated,  as  the  tension  of  the  currents  is  greater.  Silk  cov- 
erings are  excellent ;  but,  as  they  cost  too  much,  cotton  is 
used,  and  the  insulation  is  made  complete  by  means  of  a 
coating  composed  of  bitumen  of  Judea,  dissolved  in  turpen- 
tine. A  little  wax  and  resin  is  sometimes  added.  Some  ma- 
chines owe  a  part  of  their  superiority  to  the  extreme  care 
exercised  in  insulating  all  their  parts. 


THEORETICAL  PRINCIPLES   OF  MACHINES.  225 

The  arrangement  of  tlie  armature  coils  with,  reference  to 
the  field  magnets  has  given  rise  to  many  combinations,  which 
can  be  grouped  under  four  principal  classes  : 

1.  Machines  in  which  the  axes  of  the  bobbins  are  parallel 
to  the  axis  of  rotation  (Clarke,  Alliance,  Holmes,  Maude t, 
Wallace,  etc.). 

2.  Those  in  which  the  axis  of  the  single  bobbin  is  perpen- 
dicular to  the  axis  of  rotation  (Siemens,  Wilde,  Ladd). 

3.  Those  in  which  the  axes  of  the  bobbins  form  a  circle 
concentric  with  the  axis  of  rotation  (Gramme,  Heifner,  Yon 
Alteneck,  De  Meritens,  Brush,  Schuckert,  Burgin,  etc.). 

4.  Those  in  which  the  bobbins  have  their  axes  radiating 
from  the  axis  of  rotation  (Lontin).* 

It  may  here  be  stated  that  it  is  the  third  type  of  machine 
that  seems  to  utilize  most  perfectly  the  magnetic  power  of  the 
field  magnets. 

The  instantaneous  currents  produced  in  the  induced  bob- 
bins are  of  opposite  direction,  as  the  movement  always  in- 
cludes a  period  of  approach  to,  and  departure  from,  the  field 
magnets.  These  two  directions  are  themselves  reversed  ac- 
cording to  the  nature  of  the  pole  before  which  the  movement 
takes  place :  thus,  the  approach  to  a  north  pole,  and  the  de- 
parture from  a  south  pole,  give  currents  of  certain  directions ; 

*  [The  common  classification  of  armatures,  according  to  their  form,  is:  1,  disk 
armatures;  2,  ring  armatures;  3,  drum  armatures;  4,  polar  armatures.  In  the 
authors'  classification,  the  ring  and  drum  armatures  are  grouped  together  under 
3 ;  Class  1  refers  to  disk  armatures;  2,  to  the  double  T-armature  of  Siemens;  and 
4,  to  polar  armatures. 

On  the  basis  of  the  relation  of  the  magnetic  field  to  the  moving  coils,  Profes- 
sor Sylvanus  P.  Thompson  has  divided  dynamos  into  the  three  following  classes : 

CLASS  I. — u  Dynamos  in  which  there  is  rotation  of  a  coil  or  coils  in  a  uniform 
field  of  force." 

Machines  of  this  class  are  all  continuous-current  machines,  and  their  arma- 
tures are  usually  of  either  the  ring  or  drum  form. 

CLASS  II. — "  Dynamos  in  which  there  is  translation  of  coils  to  different  parts 
of  a  complex  field  of  varying  strength,  or  of  opposite  sign.  Most,  but  by  no 
means  all,  of  the  machines  of  this  class  furnish  alternate  currents." 

CLASS  III. — "  Dynamos  having  a  conductor  rotating  so  as  to  produce  a  con- 
tinuous increase  in  the  number  of  lines  of  force  cut,  by  the  device  of  sliding  one 
part  of  the  conductor  on  or  round  the  magnet,  or  on  some  other  part  of  the  cir- 
cuit.1' 

Faraday's  disk  machine  is  an  example  of  a  machine  of  this  class.  The  first 
two  classes  comprise  all  the  dynamos  which  have  commercial  value  as  genera- 
tors, the  remaining  class  being  unimportant  from  this  point  of  view.] 


226  PRODUCTION  OF  ELECTRIC   CURRENTS. 

the  approach,  to  a  south  pole,  and  departure  from  a  north 
pole,  give  currents  of  the  opposite  directions  to  those  of  the 
preceding  currents. 

These  currents  are  collected  just  as  they  are  produced,  by 
the  aid  of  metal  rings,  serving  as  intermediaries  between  the 
rotating  circuit  and  the  extremities  of  the  stationary  out- 
er circuit,  which  are  fixed.  These  rings  are  of  brass,  and 
fastened,  with  proper  insulation,  upon  the  shaft  of  the  ma- 
chine in  the  movement  of  which  they  partake ;  they  are 
each  connected  with  one  of  the  extremities  of  the  moving  cir- 
cuit, and  convey  the  currents  to  the  outer  circuit  by  means 
of  metallic  rubbers,  the  pressure  of  which  is  regulated  by 
springs.  This  is  the  arrangement  adopted  for  alternating- 
current  machines  in  which  the  armature  is  movable.  In  ma- 
chines powerful  enough  to  have  the  coils  of  their  armatures 
divided  into  several  groups,  each  giving  a  utilizable  current, 
there  must  be  as  many  pairs  of  rings  as  there  are  distinct  cir- 
cuits. 

We  shall  see,  further  on,  that  in  some  recent  machines, 
with  alternating  currents,  this  order  of  parts  has  been  re- 
versed— the  inducers  or  field  magnets  moving,  and  the  in- 
duced circuits  being  stationary  ;  these  last  are  then  connected 
directly  with  the  field  magnets,  and  there  is  only  one  pair  of 
rings  for  the  entrance  and  exit  of  the  magnetizing  current. 

It  will  be  understood  that  in  most  applications  of  elec- 
tricity alternating  currents  can  not  be  used,  because  the  work 
performed  while  the  current  passes  in  one  direction  will  be 
destroyed  by  the  next  current  which  passes  in  the  opposite 
direction.  Thus  they  can  only  be  used  in  the  production  of 
the  electric  light,  where  they  have  the  advantage  of  causing 
equal  consumption  of  the  carbon  electrodes,  and  we  have 
seen  that  this  condition  is  indispensable  for  parallel  carbon- 
burners  or  for  electric  candles. 

For  all  other  applications  it  is  indispensable  to  render  the 
currents  continuous — that  is  to  say,  to  collect  them — so  that 
they  shall  succeed  each  other  in  the  same  direction ;  thus 
there  is  attained  a  current,  which  really  is  not  continuous, 
like  a  battery-current,  but  which  is  almost  the  same  thing, 
and  produces  the  same  effects,  on  account  of  the  rapid  suc- 
cession of  the  partial  currents  which  make  it  up,  and  which 
may  be  as  many  as  fifty  to  sixty  thousand  in  a  single  minute. 
These  continuous  currents  are  also  used  for  the  electric  light 


THEORETICAL  PRINCIPLES  OF  MACHINES.  227 

with  advantage ;  the  plant  is  more  simple,  the  machines  do 
not  produce  the  hissing  which  is  telephonically  transmitted 
to  the  lamps,  and  whose  inconvenience  we  have  already  spoken 
of.  These  same  currents  are  preferable  for  open-air  incan- 
descent lamps,  and  are  used  exclusively  for  vacuum  incandes- 
cent lamps. 

In  the  early  machines,  such  as  those  of  Clarke,  whose  bob- 
bins are  wound  in  opposite  directions,  and  in  machines  whose 
induced  circuit  is  formed  of  a  Siemens  armature  (Siemens, 
Ladd,  Wilde),  there  are  only  two  changes  of  direction  of  the 
currents,  and,  to  effect  these,  a  very  simple  mechanism  suf- 
fices, called  a  commutator.  It  is  a  ferule  of  ivory,  on  which 
are  fastened  two  half-ferules  of  copper,  insulated,  and  at- 
tached each  one  to  the  extremities  of  the  moving  circuit ; 
they  turn  with  it,  and,  at  each  reversal  of  the  current,  bring 
the  terminals  of  this  circuit  before  the  corresponding  termi- 
nals of  the  exterior  circuit,  terminating  for  this  purpose  in 
two  rubbers. 

As  soon  as  the  number  of  armature  coils  was  increased  so 
as  to  increase  the  power  of  the  machine,  the  old  commutator 
became  insufficient.  The  commutator-plates  needed  to  be  in- 
creased in  number,  and  it  became  the  collector •,*  used  univer- 
sally to-day. 

To  understand  how  this  commutator  can  gather  the  cur- 
rents and  give  them  all  the  same  direction,  we  must  examine 
the  action  which  takes  place  in  an  induced  coil  in  movement. 
To  make  this  examination  easier,  we  shall  represent  the  ma- 
chine by  diagram  etrical  figures,  and  shall  employ  the  signs  -f- 
and  —  to  indicate  the  polarity  of  the  inductors  and  the  direc^ 
tion  of  the  currents. 

Let  us  consider,  first,  a  copper  wire  wound  upon  a  drum 
turning  between  the  poles  of  an  electro-magnet :  every  time 
that  the  parts  of  a  wire  situated  at  the  extremity  of  the  same 
diametrical  plane  pass  before  the  poles,  induction  will  cause 
currents  of  opposite  direction  to  be  started,  this  direction  de- 
pending on  the  nature  of  the  pole  and  direction  of  the  move- 

*  [The  distinction  made  by  the  authors  is  not  observed  in  English.  The  name 
commutator  is  given  to  the  device  by  which  the  successive  opposed  currents  are 
directed  so  as  to  follow  one  another  continuously  in  the  circuit,  irrespective  of 
whether  it  has  few  or  many  plates.  The  word  collector  is  used  only  to  denote 
the  similar  portion  of  an  alternating-current  machine,  by  which  the  currents  are 
simply  collected.] 


228  PRODUCTION  OF  ELECTRIC  CURRENTS. 

ment,  and  it  is  in  the  plane  passing  through  the  poles  and 
through  the  axis  of  rotation  that  the  action  will  be  most 
energetic  ;  it  is  there  that  the  lines  of  force  cut  by  the  wires 
are  the  most  numerous.  But  as  the  wires  form  part  of  a  cir- 
cuit, the  direction  of  the  winding  of  this  wire,  referred  to  the 
inductors  before  which  it  moves,  must  be  taken  into  account : 
if  it  presents  itself  in  one  relation  in  approaching  the  poles, 
it  will  have  the  opposite  relation  in  leaving  them  ;  it  is  as  if 
the  winding  of  the  first  period  had  been  reversed  for  the 
second  ;  it  follows  that  in  this  last  period  the  current,  which 
in  an  insulated  wire  should  be  of  the  opposite  direction,  ac- 
cording to  Faraday's  law,  becomes  redirected  as  far  as  this 
branch  of  the  helix  is  concerned,  and  takes  the  same  direction 
as  that  given  during  the  first  period  of  movement.  In  a  word, 
in  this  case  the  currents  produced  in  the  branches  of  the 
helix  under  the  influence  of  the  same  pole  have  the  same 
direction  before  and  after  their  passage.  As  the  respective 
influences  of  each  of  the  poles  neutralize  each  other  in  a 
second  plane  or  section  perpendicular  to  the  first,  and  also 
passing  through  the  axis  of  rotation,  the  change  of  direction 
of  the  currents  induced  will  take  place  each  time  they  pass 
from  one  side  to  the  other  of  this  plane,  which  is  termed 
the  commutation  plane.  The  wire  wound  around  the  drum 
will  be  divided  into  two  halves,  placed  on  each  side  of  this 
plane,  and  simultaneously  traversed  by  equal  currents  but  of 
opposite  direction. 

If,  in  place  of  a  drum,  a  cylindrical  ring  be  employed  as 
a  core  on  which  to  wind  the  wire  (Fig.  143),  the  effects  will  be 
the  same ;  only  the  portions  of  the  wire  placed  within  the 
ring  will  be  the  seat  of  currents  opposed  to  those  of  the  ex- 
terior wires,  but  of  more  feeble  ones  because  farther  removed 
from  the  poles  ;  all  that  can  ever  be  collected  is  the  excess  of 
one  set  over  the  other.  But  if  the  ring  is  made  of  soft  iron, 
it  will  exercise  a  double  influence  upon  the  production  of  cur- 
rents :  on  one  hand  it  will  answer  as  a  screen  for  the  interior 
wires,  whose  induction  will  thereby  be  diminished,  while  at 
the  same  time  it  will  augment  that  of  the  exterior  wires,  be- 
cause the  magnetic  field,  concentrated  between  the  poles  and 
the  exterior  surface  of  the  ring  will  be  much  more  powerful. 
On  the  other  hand,  this  ring  will  become  magnetized ;  the 
two  poles  of  contrary  name  will  be  produced  in  it,  opposed 
to  those  of  the  electro-magnet.  These  poles  will  be  displaced 


THEORETICAL  PRINCIPLES  OF  MACHINES. 


229 


by  the  movement,  which  will  start  in  the  armature  helices  a 
second  class  of  currents,  which  M.  Du  Moncel  has  termed 
polar  interversion  currents.  These  currents  have  the  same 
direction  during  each  period  of  the  movement,  because  here 
again,  during  the  second  period,  the  action  is  produced  on 


FIG.  143. — Direct  induction  in  the  ring  armature. 

the  opposite  side  of  the  helices,  which  amounts  to  changing 
the  direction  of  the  winding.  As  this  direction  is  the  same 
as  that  of  the  currents  produced  at  the  same  moment  by  the 
direct  induction,  the  two  currents  are  added  to  each  other  so 
as  to  form  a  single  one  of  increased  intensity. 

Like  the  drum  first  spoken  of,  the  ring  is  divided  into 
two  halves,  in  which  the  helices  are  traversed  by  equal  and 
opposed  currents,  which  are  in  equilibrium  in  the  plane  of 
commutation  A  A.  By  connecting  all  the  helices  in  tension 
— that  is  to  say,  the  entrance  end  of  one  with  the  exit  end 
of  the  other — they  can  be  considered  as  forming  two  bat- 
teries, composed  of  the  same  number  of  similar  elements, 
connected  by  their  like  poles ;  that  is  to  say,  two  batteries 
in  opposition.  The  two  positive  poles  must  then  be  put  in 
communication  by  means  of  a  rubber,  F,  with  one  of  the 
extremities  of  an  exterior  circuit,  and  the  two  negative  poles 
with  the  other  extremity  by  a  second  rubber,  F',  for  a  cur- 
rent to  be  established ;  this  current  will  be  formed  by  those 
of  the  two  halves  of  the  ring,  which  will  thus  be  coupled  for 
quantity. 


230 


PRODUCTION  OF  ELECTRIC  CURRENTS. 


On  account  of  the  movement  of  the  induced  helices,  each 
one  of  them  passes  necessarily  from  one  side  to  the  other  of 
the  commutation  plane,  and  consequently  the  currents,  of 
which  it  is  the  seat,  change  their  direction.  The  ring  is  always 
divided  into  two  halves,  but  these  do  not  always  contain  the 
same  helices  which  originally  constituted  them,  and  the  junc- 
tions with  the  exterior  circuit  must  be  changed.  This  is  ef- 
fected by  arranging  as  many  connecting  wires  as  there  are 
helices,  and  by  terminating  them  by  as  many  plates ;  these 
plates,  perfectly  insulated  from  each  other,  are  united  so  as 
to  form  a  little  drum,  which  constitutes  the  commutator.  It 
is  mounted  on  the  shaft  of  the  machine  and  turns  with  it,  so 
that  it  brings  the  brushes,  F  F',  necessarily  in  contact  with  the 
two  plates  which  correspond  to  the  helices  reaching  the  com- 
mutation plane. 

We  have  seen  that  the  induced  helices  are  subjected  to  a 
double  effect  of  induction,  one  produced  directly  by  the  poles 
of  the  field  magnet,  the  other  by  the  change  of  magnetic 


'-•-•E 


FIG.  144. — Indirect  induction,  or  induction  by  magnetic  reaction  of  the  radiating 

armature- cores. 

state  of  the  core.  What  has  just  been  said  applies  to  cases 
where  the  first  effect  preponderates  ;  it  is  different  where  the 
core  reaction  predominates  (Fig.  144).  Then  the  inversions 
take  place  at  the  moment  of  passage  in  front  of  the  poles, 
because  it  is  at  this  moment  that  the  magnetization  and 
demagnetization  of  the  cores  are  produced.  In  this  case  the 
plane  of  commutation,  and  with  it  the  points  of  contact  of  the 


THEORETICAL  PRINCIPLES  OF  MACHINES.  231 

brushes  upon  the  collector,  becomes  one  with  the  plane  S  N, 
passing  through  the  poles. 

The  currents  due  to  direct  induction  still  exist,  though 
they  are  much  weaker,  because  the  way  in  which  the  helices 
come  before  the  magnet  is  much  less  favorable.  As  their 
commutation  plane  is  not  the  same,  they  can  not  be  collected, 
and  they  cause  in  the  machine  the  production  of  heat,  which 
increases  that  developed  in  the  cores  by  the  molecular  move- 
ments due  to  change  of  polarity  ;  thus  machines  of  this  class 
have  their  speed  limited  by  the  heating. 

Up  to  this  point  we  have  not  taken  into  account  the  gal- 
vanic field  which  results  from  the  currents  of  induction,  and 
which  reacts  upon  the  magnetic  field  of  the  inductors.  In 
consequence  of  this  reaction,  the  plane  in  which  induction  is 
most  powerful  is  displaced  ;  in  the  machines  we  are  now  dis- 
cussing, and  which  are  intended  for  the  production  of  cur- 
rents, the  displacement  is  in  the  direction  of  the  movement, 
as  the  reaction  is  dependent  upon  the  existence  of  these  cur- 
rents, and  increases  in  proportion  as  they  attain  their  maxi- 
mum intensity.  It  is,  then,  in  a  different  position,  A'  A'  or 
S7  N',  to  be  determined,  that  the  real  plane  of  commutation  is 
situated,  and  consequently  the  contacts  of  the  brushes  on  the 
commutator. 

When  the  reversibility  of  these  machines  is  utilized  so  as 
to  transform  them  into  motors — that  is,  when  the  armature  re- 
ceives an  electric  current  from  an  external  source — and  when 
its  movement  is  due  to  the  reciprocal  actions  of  the  inducers 
and  of  the  current,  this  displacement  of  the  magnetic  field 
takes  place  in  a  direction  the  reverse  of  the  movement,  as  the 
galvanic  field  exists  permanently,  and  can  act  before  reaching 
the  inducing  poles.  In  both  cases  this  displacement  causes 
that  of  the  plane  of  commutation,  and  consequently  of  the 
points  of  contact  of  the  brushes  upon  the  commutator.  It 
will  sometimes  be  found,  on  examining  a  machine  at  work, 
that  the  apparent  points  of  contact  do  not  correspond  with  the 
place  that  they  should  occupy  theoretically  ;  the  requirements 
of  construction  making  it  necessary  to  seek  a  new  position  for 
them,  by  bending  the  wires  which  connect  the  plates  of  the 
commutator  with  the  armature  coils. 


232 


PRODUCTION   OF  ELECTRIC  CURRENTS. 


CHAPTER  Y. 

THE  FIRST  MAGNETO-ELECTRIC  MACHINES. 

THE  discoveries  of  Faraday  were  quickly  utilized  in  the  de- 
vising of  apparatus  to  produce  induced  currents  in  a  continu- 
ous manner.  In  the  year  1832  Pixii  constructed  in  Paris  an 
early  machine  (Fig.  145)  in  which  a  permanent  magnet  turned 

in  front  of  the  poles  of  an 
electro-magnet ;  the  soft- 
iron  cores  of  this  last  one 
were  thus  magnetized  and 
demagnetized  successive- 
ly, and  created  in  the  cop- 
per wire  surrounding  them 
alternating  induced  cur- 
rents; these  currents,  given 
the  same  direction  by  a 
commutator  fixed  on  the 
axis  of  rotation,  were  so 
intense  that,  in  Ampere's 
lectures  at  the  Sorbonne, 
they  could  decompose  the 
water  in  a  voltameter,  and 
redden  a  platinum  wire. 
His  first  magneto-electric 
machine  is  preserved  to- 
day in  the  cabinet  of  the 
Conservatoire  des  Arts  et 
Metiers. 

In  1833  an  American 

named  Saxton  modified  Pixii's  machine  by  making  the  per- 
manent magnet  fixed,  and  having  the  much  lighter  electro- 
magnet rotate.  The  following  year  Clarke  put  in  practice 
the  same  idea,  placing  the  magnet  in  a  vertical  position,  and 
turning  the  electro-magnet  laterally  (Fig.  146).  In  spite  of 
the  slight  importance  of  this  change,  it  is  Clarke's  name  that 
is  used  to-day  to  designate  this  class  of  apparatus,  employed 
now  more  particularly  as  illustrative  of  the  science,  in  the 
lecture-room. 


FIG.  145.— Magneto-electric  machine  of  Pixii, 
1832. 


THE  FIRST  MAGNETO-ELECTRIC  MACHINES. 


233 


I.   NOLLET. — VAN  MALDEREN. — HOLMES. 

It  seemed  quite  natural  to  increase  the  number  of  coils  of 
Clarke's  machine,  for  the  purpose  of  obtaining  stronger  cur- 
rents. This  was  done  in  1849  by  Nollet,  Professor  of  Physics 
in  the  Military  School  of  Brussels.  He  first  doubled  the  num- 
ber of  coils  ;  then  he  arranged  eight  upon  a  wooden  cylinder, 
and  turned  them  between  the  arms  of  four  magnets  opposite 
each  other  in  pairs.  He  finally  arranged  sixteen  on  the  same 
disk  turning  between  the  arms  of  eight  magnets,  and,  placing 

together  several  disks  upon  the 
same  axis,  he  created  the  mag- 
neto-electric machine  well  known 
under  the  name  of  the  Alliance 
machine  (machine  de  V Alliance]. 
The  decomposition  of  water  by 
electric  currents  had  already  sug- 
gested the  idea  of  doing  it  on  a 
large  scale,  and  of  using  for  light- 
ing the  gas  obtained  by  the  aid 
of  powerful  magneto-electric  ma- 
chines. They  were  thus  to  in- 
directly produce 
light.  It  is  not 
difficult  to  under- 
stand that  the 
proposed  specu- 
lation came  to 
naught ;  the  ma- 
chine consumed 
too  much  power, 
and  it  was  sim- 
pler and  cheaper  to  extract  the  illuminating  gas  directly  from 
bituminous  coal.  Besides,  it  was  necessary  to  render  the  cur- 
rents continuous,  and  all'  the  commutators  tried  were  rapidly 
used  up  by  the  circuit-breaking  sparks.  It  was  after  this, 
toward  1856,  that  M.  Du  Moncel  advised  the  use  of  the 
machine  for  the  production  of  the  electric  light,  and,  thanks 
to  the  idea  suggested  by  M.  Masson,  the  commutator  was  sup- 
pressed. It  was  then  even  by  accident  that  for  this  use  alter- 
nating currents  were  employed  whose  special  advantages  in 
certain  systems  of  lighting  we  have  already  described.  The 


FIG.  146.— Magneto-electric  machine  of  Clarke. 


234:  PRODUCTION  OF  ELECTRIC   CURRENTS. 

success  was  as  complete  as  was  possible,  and  it  is  tlie  first 
machine  that  was  put  to  industrial  use,  principally  the  appli- 
cation of  the  electric  light  to  light-houses,  inaugurated  in 
France  in  1863. 

In  this  machine  the  inductors,  or  field  magnets,  are  station- 
ary ;  they  consist  of  two  parallel  rings  of  eight  horseshoe 
magnets,  placed  radially  around  disks ;  these  magnets  are 
supported  by  wooden  bars,  and  their  poles,  very  regularly 
spaced,  are  alternated  so  that  a  north  pole  is  opposed  to  a 
south  pole,  and  so  on  ;  each  of  these  magnets  is  composed  of 
six  steel  plates,  one  centimetre  thick,  supplied  by  the  Allevard 
Works ;  these  plates  are  tempered,  polished  on  a  stone,  and 
fastened  together  by  screws  ;  they  are  separately  magnetized, 
and  each  set,  weighing  about  twenty  kilogrammes,  can  lift 
sixty. 

The  armature  coils  are  movable  ;  they  are  arranged  around 
a  brass  disk  by  means  of  collars,  and  parallel  to  the  axis  of 
rotation  ;  the  spaces  between  them  are  regulated  with  the  ut- 
most precision,  so  that  they  all  come  at  all  times  in  the  same 
relative  positions  with  reference  to  the  sixteen  poles  of  the 
field  magnets. 

The  cores  of  Clarke's  armature  bobbins  were  made  of  soft- 
iron  rods ;  but  when  they  are  caused  to  turn  much  faster  in 
the  presence  of  very  powerful  magnets,  they  need  some  modi- 
fication to  enable  them  to  be  magnetized  and  demagnetized 
more  rapidly  without  heating. 

We  have  already  stated  that  the  rapid  changes  of  polar- 
ity cause  molecular  movements  in  the  metal,  accompanied 
by  a  production  of  heat ;  we  have  also  seen  that  induced  cur- 
rents are  produced  in  the  cores  like  those  whose  existence 
was  shown  by  Faraday,  and  that  to  diminish  their  strength, 
and  facilitate  the  effects  of  the  magnetic  influence,  the  mate- 
rial of  the  cores  had  to  be  diminished  and  divided  as  much  as 
possible. 

This  has  been  done  with  the  Alliance  machines  by  mak- 
ing the  cores  of  iron  tubes  split  longitudinally.  The  washers 
of  brass,  fastened  at  each  end  to  keep  the  wire  in  place,  are 
also  split  in  a  radial  line.  On  this  tube  the  wires  are  wound 
with  proper  insulation ;  at  first  too  fine  a  wire  was  used, 
which  became  heated  and  developed  a  high  resistance  ;  it 
became  necessary,  for  the  sake  of  increasing  the  section,  to 
wind  several  parallel  to  each  other  ;  instead  of  one,  four  were 


236  PRODUCTION  OF  ELECTRIC   CURRENTS. 

first  substituted  ;  to-day  eight  wires,  of  one  millimetre  diam- 
eter, are  used. 

There  is  no  need,  as  we  have  already  stated,  to  consider 
the  production  of  electricity  in  these  machines ;  it  is  clear 
that  the  currents  change  in  direction  every  time  the  bobbins 
pass  before  the  poles  of  the  magnet :  as  there  are  sixteen 
magnet-poles,  there  are  sixteen  changes  of  current  in  each 
revolution,  so  that  with  a  speed  of  four  hundred  revolutions 
per  minute  there  are  over  one  hundred  reversals  per  second. 
Every  time  the  currents  change  their  direction  the  voltaic  arc 
ceases  to  exist ;  the  continuity  of  the  light  is  due  to  the  in- 
candescence of  the  polar  carbons ;  the  duration  of  these  in- 
terruptions is,  moreover,  so  short — hardly  the  ten-thousandth 
of  a  second — that  the  arc  easily  starts  anew  through  the  air 
heated  by  the  radiation  from  the  incandescent  carbons,  and 
the  more  so  as  the  reversals  take  place  precisely  when  the  cur- 
rents attain  their  maximum  of  intensity. 

Nollet  died  in  the  midst  of  his  work,  and  it  was  Van  Mal- 
deren,  his  collaborator,  appointed  engineer  of  the  company, 
who  gave  the  machines  their  last  improvements  ;  thanks  are 
due  to  him  for  the  success  then  obtained,  whose  promises 
were  never  destined  to  be  realized  ;  the  hour  of  electric  light- 
ing had  not  yet  come. 

About  the  same  period  M.  Holmes,  who  had  assisted  in 
the  construction  of  Collet's  machines  ordered  from  England 
for  the  production  of  illuminating  gas,  succeeded  on  his  own 
part  in  utilizing  them  for  the  production  of  the  electric  light. 
The  same  appears  to  have  happened  to  the  Compagnie  V Al- 
liance, and  it  is  with  one  of  these  machines,  which  were  built 
between  1858  and  1862,  that  the  first  experiments  with  electric 
light  in  the  Dungeness  light-house  were  conducted  ;  the  results 
were  not  very  good,  because  the  commutator  for  rendering  the 
currents  continuous  was  still  in  use. 


"II.  SIEMENS. — WILDE. — LADD. 

At  this  epoch  it  was  principally  from  the  changes  in  the 
magnetic  state  of  the  cores  that  the  current  was  produced.  To 
develop  still  more  this  method  of  induction,  and  obtain  from 
it  the  most  powerful  effects,  Mr.  W.  Siemens  invented  in  1854 
the  ingenious  armature  which  bears  his  name  (Fig.  148).  It 
is  formed  of  a  cylindrical  core  of  soft  iron,  with  two  longi- 


THE  FIRST  MAGNETO-ELEOTEIC  MACHINES. 


237 


tudinal  grooves  cut  in  it,  which  gives  it  the  section  of  a  double 
T  (Fig.  149).  The  wire  that  is  subjected  to  induction  is  wound 
in  the  grooves  which  it  fills  so  as  to  restore  the  cylindrical 
form  ;  binding- wires  prevent  the  wire  yielding  to  the  centrifu- 


FIG.  148. — Siemens'  armature. 


gal  force.     The  wings  of  the  double  T  form  poles  extending 
along  the  core  and  reacting  energetically  on  the  wires. 

This  armature  was  first  designed  for  a  telegraphic  induc- 
tion apparatus.  But  in  1866  Mr.  Siemens  employed  it  in  the 
construction  of  a  small  magneto-electric  machine.  The  poles 
of  the  field  magnets  are  united  by  a  piece  of  brass  ;  the  arma- 
ture turns  in  a  cylindrical  cavity,  between  these  three  pieces, 
which  completely  surround  it ;  a  commutator  serves  to  render 
the  currents  continuous,  whose  commuta- 
tion  plane  passes  through  the  plane  of  the 
poles,  subject,  however,  as  before  explained, 
to  the  displacement  due  to  the  working  of 
the  machine.  In  the  Electrical  Exhibition 
at  Paris  there  could  be  seen  Mr.  Siemens's 
original  model,  as  well  as  two  more  power- 
ful machines  of  the  same  type  which  had 
been  exhibited  in  1873  at  the  Vienna  Exhi- 
bition. This  armature  had  then  been  dis- 
carded as  an  organ  for  development  of  cur- 
rents, because  of  the  enormous  speed  needed, 
and  the  great  heat  which  was  developed  in  it.  Nevertheless, 
it  is  still  employed  with  success  in  small  electro-motors. 

It  is  with  the  Siemens  armature  that  M.  Wilde  constructed 
one  of  the  two  machines  which  had  such  a  success  at  the 
Paris  Exhibition  of  1867  ;  the  second  was  the  machine  of  Mr. 
Ladd,  of  which  we  shall  speak  further  on. 

It  is  M.  Wilde  who,  struck  with  the  enormous  superiority 
of  electro-magnets  over  permanent  magnets  of  the  same 
weight,  first  conceived  the  idea  of  using  them  in  the  field  as 
inductors.  Wilde's  machine,  then,  was  the  first  dynamo- 
electric  machine ;  it  was  composed  (Fig.  150)  of  a  large  Sie- 


I 

FIG.  149.— Cross-sec- 
tion of  the  Siemens 
armature. 


238 


PRODUCTION  OF  ELECTRIC  CURRENTS. 


mens  armature,  turning  between  the  poles  of  a  powerful  ver- 
tical electro-magnet,  arranged  as  we  have  seen  in  explaining 
the  employment  of  this  armature.  The  magnetizing  or  ex- 
citing current  of  the  field  was  furnished  by  a  small  Siemens 
magneto -electric  machine,  placed  above  the  first  named ;  the 


FIG.  150. — Wilde's  first  dynamo-electric  machine,  with  Siemens'  magneto-electric  exciter. 

movement  was  transmitted  separately  by  pulleys  to  each  of 
two  bobbins,  whose  speed  reached  2,400  turns  per  minute  for 
the  small  bobbin  and  1,500  turns  for  the  large  one.  At  the 
same  time  (1867)  Mr.  Ladd  constructed  a  similar  machine, 
but  with  an  improvement ;  the  small  special  exciting  machine 
was  suppressed  in  part,  and  the  inducers  or  field  magnets  of 


THE  FIRST  MAGNETO-ELECTRIC  MACHINES.  239 

the  large  machine  were  utilized  to  influence  both  bobbins  at 
once.  To  this  end  the  field  magnets  were  formed  of  two 
large,  flat,  horizontal  bobbins,  placed  one  above  the  other  and 
connected  so  as  to  have  their  opposite  poles  facing  each  other. 
The  cores  terminated  at  each  extremity  in  polar  masses, 
shaped  so  as  to  receive  the  armatures.  In  a  second  model  Mr. 
Ladd  suppressed  the  special  exciting  armature,  only  preserv- 
ing a  single  one  with  two  distinct  circuits — one  furnishing  the 
exciting  current,  the  other  supplying  the  exterior  circuit. 

This  method  of  utilizing  the  reaction  on  the  field  magnets 
of  the  currents  which  they  themselves  produced  had  also 
been  applied  some  time  before  by  M.  Wilde  to  another  type 
of  machine  resembling  Collet's.  In  this  machine  the  field 
magnets  are  formed  by  thirty-two  straight  electro-magnets, 
arranged  in  a  circle  on  a  frame  and  forming  two  parallel 
series  whose  alternate  poles  are  placed  in  front  of  each  other. 
In  the  space  between  them  a  plate  carrying  sixteen  armature 
coils  on  each  side  rotates. 

The  field  magnets  are  excited  by  a  current  taken  from  four 
of  these  coils  and  rendered  continuous  by  means  of  a  commu- 
tator. The  current  of  the  other  induced  bobbins  is  collected 
on  two  friction-rings  and  sent  into  the  lamp  circuit.  This 
machine,  which  received  several  applications  in  England,  had 
been  long  abandoned  in  France  by  the  company  that  had 
bought  it  in  1867.  It  was  taken  up  again  last  year  (1879),  in 
spite  of  the  inconveniences  of  its  commutator,  and  quite  satis- 
factory results  obtained  with  it. 

These  different  improvements  were  merely  the  application  \ 
of  principles  which  Mr.  Yarley  had  embodied  in  a  machine 
patented  by  him  in  1866,  and  which  Messrs.  Werner  Siemens 
and  Wheatstone  had  explained  in  two  communications  pre- 
sented in  that  year  to  the  Academy  of  Sciences  of  Berlin  and 
to  the  Royal  Society  of  London.*  The  first  memoir  showed 
that  electric  energy  could  be  converted  into  magnetic  energy 
without  the  need  of  permanent  magnets  ;  the  second  memoir 
showed  that  the  power  of  an  electro-magnet,  which  retained 
a  trace  of  residual  magnetism,  could  be  developed  up  to  satu- 
ration by  the  progressive  increase  of  the  induction  currents 
produced  by  itself. 

This  succession  of  discoveries  was  the  starting-point  of  the  -  -  o  v>^ 

*  The  principle  of  "  self- excitation  "  was  first  enunciated  by  a  Dane,  Soren 
Hjorth,  who  patented  in  England  in  1854  a  machine  in  which  it  was  carried  out. 
17 


210  PRODUCTION   OF  ELECTRIC  CURRENTS. 

rapid  progress  witnessed  by  onr  own  eyes,  and,  thanks  to 
which,  we  have  succeeded  in  effecting  at  pleasure  all  those 
wonderful  transformations  of  an  agent  which,  always  invisi- 
ble and  elusive,  only  manifests  itself  in  its  prodigious  effects 
of  heat,  work,  and  electricity. 


CHAPTER  VI. 

THE  GRAMME  MACHINES. 

M.  GKAMME  is  the  first  inventor  who  succeeded  in  practi- 
cally developing  these  discoveries,  and  in  making  all  the  fac- 
tors unite  in  producing  electricity  with  the  regularity  and 
economy  indispensable  in  industrial  applications.  It  is  in 
great  part  to  the  machine  of  this  indefatigable  worker  that 
the  development  of  electric  lighting  is  due. 

M.  Gramme's  improvements  apply  to  all  parts  of  the  ma- 
chine ;  the  power  of  the  field  magnets  has  been  brought  to  a 
maximum  by  the  use  of  electro-magnets  with  consequent  poles. 
The  annular  form  given  to  the  induced  circuit  has  enabled  us 
to  utilize  uninterruptedly  the  action  of  induction,  and  the 
currents  have  been  collected  and  rendered  continuous  very 
successfully,  thanks  to  the  ingenious  arrangement  of  the  col- 
lector. These  machines  have  received,  besides,  since  their  in- 
vention, numberless  alterations  ;  successively  electro-magnetic 
machines  (Fig.  151)  and  dynamo-electric  machines  have  been 
constructed,  something  which  is  effected,  as  we  have  already 
seen,  without  difficulty.  The  field  magnets  were  placed  ver- 
tically in  the  first  machines  (Fig.  152),  they  are  now  hori- 
zontal, without  other  reason  than  the  convenience  of  con- 
struction ;  finally  the  ring,  after  having  been  made  duplex, 
so  as  to  furnish  separately  the  exciting  and  the  working  cur- 
rents, has  been  reduced  to  a  single  circuit,  whose  entire  cur- 
rent traverses  the  coils  of  the  field  magnets.  We  shall  limit 
ourselves  to  the  description  of  the  latest  model,  designated 
workshop  type  (type  $  atelier),  which  is  the  one  most  gener- 
ally used  (Fig.  153). 

The  inductor,  or  field  magnet,  is  composed  of  two  horizon- 
tal bars  connected  by  bolts  with  the  frame.  The  whole  forms 


THE  GRAMME  MACHINES.  241 

two  electro-magnets  with  their  two  arms,  united  by  similar 
poles,  producing  in  the  middle  of  the  system  two  double  or 
consequent  poles  of  great  energy,  between  which  the  ring 
turns.  The  cast-iron  upright  frame  serves  at  once  as  support 


FIG.  151. — Gramme  magneto-electric  machine  for  the  laboratory. 

for  the  parts  of  the  machine  and  as  a  yoke  for  the  electro- 
magnets, whose  magnetic  circle  they  complete.  Although  the 
residual  power  of  cast-iron  is  considerable,  its  use  is  attended 
with  no  inconvenience,  provided  the  pieces  have  to  under- 
go no  change  of  polarity.  It  is  only  necessary  to  take  into 


242 


PRODUCTION   OF  ELECTRIC  CURRENTS. 


account  the  fact  that  the  magnetic  capacity  of  cast-iron  is 
less  than  that  of  wrought-iron,  and  to  increase  the  dimen- 
sions in  constructing  the  machine. 


FIG.  152. — First  form  of  Gramme  dynamo  machine  for  lighting. 

The  armature  is  formed  of  a  flat  annular  core,  constructed 
of  iron  wire,  rolled  into  a  circular  shape  by  a  special  mill ;  the 
use  of  iron  wire  is  for  the  purpose  of  subdividing  the  mass 


THE  GRAMME  MACHINES. 


243 


of  metal,  the  necessity  of  which,  we  have  already  spoken  of. 
On  this  core  are  wound  transversely  several  layers  of  copper 
wire,  of  suitable  diameter,  most  carefully  insulated,  and  sep- 
arated into  sections  of  distinct  helices,  placed  side  by  side. 
Fig.  154  shows  it  complete  in  one  part  only ;  the  other  part 
has  the  half  of  the  helices  removed,  and  farther  on  the  ring 
is  cut  so  as  to  show  the  section  of  the  iron  wires  composing 
it.  All  the  coils  are  connected  for  tension,  the  inner  end  of 
one  and  the  outer  end  of  the  other  being  attached  to  the  same 


FIG.  153. — Gramme  machine  (workshop  type). 

plate  of  copper.  Thus  there  are  as  many  plates  as  coils,  and 
naturally  the  division  is  made  with  an  even  number,  so  that 
the  two  halves  of  the  ring  may  always  contain  the  same  num- 
ber of  coils.  All  the  plates,  also  insulated,  are  prolonged 
back  of  the  ring,  and  there  form  a  small  drum  which  consti- 
tutes the  commutator. 

The  two  rubbers  are  a  species  of  brush  or  broom  made  of 
wires  of  a  good  conducting  metal ;  they  are  made  to  bear 
against  the  collector  by  springs,  which  can  be  regulated  by 


244 


PRODUCTION   OF  ELECTRIC  CURRENTS. 


FIG.  154.— Gramme  King. 


hand.  This  kind  of  rubbers  insures  perfect  contact,  and 
weakens  the  destructive  effects  of  the  sparks  by  dividing  them 
between  a  large  number  of  points.* 

The  collecting  apparatus  is  the  delicate  part  of  machines  ; 
the  contact  must  be  sufficient  to  insure  the  passage  of  the  cur- 
rent with  the  least  possible  resistance,  without  being  strong 

enough  for  the  friction  to 
wear  away  the  commuta- 
tor rapidly.  Moreover,  this 
friction  can  not  be  reduced 
by  the  use  of  oil,  because 
the  lubricator,  quickly  be- 
coming charged  with  me- 
tallic dust,  would  fill  up 
the  intervals  between  the 
plates  and  destroy  their  in- 
sulation. The  collector  and 
brushes  must  therefore  be 
watched  closely,  and  the 
greatest  care  taken  of  them ; 
the  points  of  contact  of  the 

brushes  with  the  collector  should  always  be  placed  exactly  in 
the  line  of  the  commutation  plane,  determined  once  for  all  at 
the  normal  running  of  the  machine,  and  exactly  at  the  ex- 
tremities of  the  same  diameter  of  the  commutator,  as  other- 
wise one  part  of  the  opposing  currents  produced  in  the  ring 
would  be  destroyed  by  a  corresponding  part  of  the  other  cur- 
rent ;  the  intensity  of  the  remaining  current  would  be  weak- 
ened in  proportion. 

We  have  seen  that  the  currents  of  these  machines  were 
produced  by  the  direct  influence  of  the  poles  of  the  field 
magnets,  and  by  the  magnetic  reactions  of  the  ring ;  their 
intensity  increases  with  the  speed  of  the  machine,  as  these 
effects  are  multiplied  in  proportion.  There  is,  however,  a 
limit  which  it  would  be  dangerous  to  exceed,  because  the  wire 
of  the  coils,  being  invariable,  would  finally  be  of  insufficient 
section  ;  the  internal  resistance  would  gradually  increase,  and 
would  cause  the  development  of  a  great  deal  of  heat ;  the  work 
expended  would  thus  increase  much  quicker  than  the  intensity 
of  the  current. 


*  [The  brushes  used  on  all  machines  in  this  country  consist  of  a  bundle  of 
strips  of  sheet-copper.] 


THE   GRAMME   MACHINES. 


245 


The  following  table,  published  by  M.  Fontaine,  shows  in 
what  proportions  the  results  vary  with  the  speed  of  the  ma- 
chine, and  with  the  distance  between  it  and  the  lamps : 

Influence  of  tlie  Speed  of  the  Macliine. 


LUMINOUS   INTENSITY   IN 

WORK1  EXPENDED  IN 

NUMBER  OF  Length  of  Distance  be- 

CAKCELS. 

KILOGKAMMETKE8. 

Number  of 

REVOLU-       the  con- 

tween  the    i 

carcels 

T1ONS  PER 
MINUTE. 

ducting 
wire. 

points  of 
the  carbons. 

Measured 
horizontally. 

Mean 
intensity. 

Total. 

Per  100  car- 
eels  of  mean 
intensity. 

per  horse- 
power. 

in. 

mm. 

TOO 

100 

3 

160 

820 

185 

57-81 

130 

725 

100 

3 

243 

486 

165 

33-95 

220 

750 

100 

3 

295 

590 

192 

32-54 

230 

800 

100 

4 

305 

730 

230 

31-65 

235 

850 

100 

5 

488 

976 

282 

28-89 

270 

900 

100 

6 

576 

1,152 

330 

28-64 

260 

1,000 

100 

10 

646 

1,292 

338 

26-16 

285 

The  mean  luminous  intensities  are  here  the  mean  of  in- 
tensities observed  at  different  angles : 

Influence  of  Distance  of  the  Lamp  from  the  Machine. 


ILLUMINATING  POWEE  IN 

WORK  EXPENDED  IN  KILO- 

NUMBER  OF 
REVOLU- 
TIONS PER 
MINUTE. 

Length  of 
conduct- 
ing wire. 

Distance  be- 
tween the 
points  of 
the  carbons. 

CAECEL8. 

GKAMMETEES. 

Number  of 
carcels 
per  horse- 
power. 

Measured 
horizontally. 

Mean 
intensity. 

Total. 

Per  100  car- 
cels of  mean 
intensity. 

m. 

mm. 

750 

100 

4 

321 

690 

186 

28-9 

267 

800 

150 

5 

345 

642 

230 

33-3 

225 

825 

200 

5 

315 

630 

232 

36-8 

178 

850 

300 

5 

275 

550 

225 

40-9 

183 

900 

400 

5 

260 

520 

241 

46'3 

162 

950 

500 

5 

245 

490 

230 

46-1 

160 

1,000 

750 

5 

236 

472 

243 

51-4 

145 

1,100 

1,000 

5 

215 

430 

256 

59-5 

126 

1,350 

2,000 

5 

160 

320 

230 

71-8 

104 

In  all  the  experiments  the  section  of  the  conducting  wire 
was  ten  square  millimetres. 

DIVISION  MACHINES  (Machines  d  Division).* 

As  soon  as  the  improvements  effected  in  regulators  by  the 
use  of  the  derived  current  made  possible  the  placing  of  sev- 

*  [This  term,  used  to  denote  machines  operating  more  than  one  lamp  on  one 
circuit,  is  quite  erroneously  applied,  as  it  refers  to  no  distinctive  mode  of  con- 
struction. The  number  of  devices  which  can  be  operated  upon  any  circuit  de- 


24:6 


PRODUCTION  OF  ELECTRIC  CURRENTS. 


eral  lamps  on  the  same  circuit,  M.  Gramme  devised  new  types 
arranged  to  furnish  the  same  results  with  continuous  cur- 
rents ;  the  field  magnets  have  received  new  polar  extensions 
of  large  section,  and  the  power  of  their  magnetic  field  is  much 


FIG.  155. — Five-light  Gramme  machine. 

increased  ;  the  armature-wire  is  much  finer  and  longer,  conse- 
quently the  electro-motive  force  is  much  greater  for  the  same 
speed,  and  the  current  possesses  the  necessary  tension  (Fig. 
155).  The  field  magnets  are  supplied  by  a  special  exciter  ;  in 

pends  solely,  so  far  as  the  machine  is  concerned,  upon  the  quantity  and  electro- 
motive force  of  the  current  furnished ;  but  this  is  a  matter  of  proportions  of 
parts  and  speed,  and  not  of  constructive  differences.  The  term  could  be  rightly 
applied  to  denote  machines  feeding  several  distinct  circuits,  but  these  are  better 
described  as  '*  multiple-circuit  machines."] 


THE   GRAMME  MACHINES. 


247 


spite  of  its  complication,  this  arrangement  has  the  advantage 
of  rendering  the  field  magnets  independent  of  variations  in  the 
resistance  of  the  exterior  circuit,  and  insures  to  the  magnetic 
field  a  stability  analogous  to  that  of  magneto-electric  machines. 
These  machines  can  supply  from  two  to  five,  ten,  and  even 
twenty  lights,  by  changing  the  speed  of  rotation  and  the  re- 
sistance of  the  conducting  wire,  as  is  shown  in  the  following 
figures,  determined  by  M.  Fontaine  ("Revue  Industrielle ") : 


i 

NUMBEK  OF 
LIGHTS. 

Number  of  revo- 
tions  per  minute. 

Resistance  of  con- 
ductor. 

Normal  length 
of  the  arc. 

Distance  of  the  car- 
bons producing 
extinction. 

ohms. 

mm. 

mm. 

1 

500 

TOO 

2'5 

6-0 

2 

700 

2-00 

2-5 

5-7 

3 

975 

3-00 

2-5 

5'5 

4 

1,125 

4-10 

25 

5'5 

5 

1,300 

6*80 

2-5 

5-5 

The  figures  of  the  last  two  columns  show  that  the  current 
should  always  possess  a  tension  superior  to  the  eifective  re- 
sistance of  the  arcs  used,  so  as  to  leave  a  sufficient  margin  for 
the  action  of  the  regulators. 

The  same  types  serve  also  for  the  production  of  the  pow- 
erful lights  in  use  in  light-houses  and  in  marine  and  war  ap- 
paratus. MM.  Sautter  and  Lemonnier,  who  construct  so  suc- 
cessfully this  class  of  machine,  have  given  a  resume  of  their 
conditions  in  the  interesting  figures  in  the  following  table  : 


TYPE  OF  MACHINE. 

WIEE3  CF  THE 
KING. 

WIBE8  OF  THE 
FIELD  MAGNET. 

Number  of 
revolutions 
per  minute. 

Mean  length 
of  arc. 

Diameter  of 
carbons. 

ILLUMINAT- 
ING POWKR. 

Work  ex- 
pended, in 
horse-power. 

Diam- 
eter. 

Length. 

DC£?:L«*>>- 

Aver- 
age. 

Maxi- 
mum. 

M  (200  carcels)    

mm. 

1-2 
1-8 
2-8 
3-65 
4-3 

1-8 
2-8 

m. 
340 
264 
336 
276 
460 

264 
336 

mm. 
1-8 
3-4 
3-4 
3-4 
3-8 

3-4 

3-8 

m. 
440 
565 

1,280 
1,280 
2,160 

565 
1,280 

1,600 
820 
675 

1,360 

475 

880 
675 

mm. 
3 
4 
4 

4-5 
6 

4 
5 

mm. 
9 
13 
18 
18 
20 

13 
18 

226 
490 
1,015 
1,241 

2,198 

1,185 

2,200 

625 
1,200 
2,500 
3,300 
6,000 

2,600 
4,000 

1-25 
2-75 

5-25 
8" 
12- 

5-50 
10-5 

AC  (600  carcels)  
CT(  1,600  carcels)  
CQ  (2,500  carcels)  
DQ  (4,000  carcels)  
2  AC  machines  coupled 
for  quantity  

2  CT  machines  coupled 
for  quantity.  .  .  . 

The  maximum  intensities  are  those  attained  by  using  lamps  inclined  so  as  to 
expose  the  crater  of  the  positive  carbon  to  the  surface  to  be  illuminated. 

The  last  two  lines,  compared  with  the  second  and  third,  show  what  an  in- 
crease of  light  follows  the  coupling  of  two  machines  for  quantity. 


248  PRODUCTION  OF  ELECTRIC   CURRENTS. 

These  powerful  machines  are  sometimes  constructed  with 
a  double  ring — that  is  to  say,  the  one  hundred  and  twenty 
coils  which  it  contains  are  divided  into  two  series — sixty  coils 
have  their  entrance  ends  on  the  right  side  and  the  others  have 
them  on  the  left.  The  machine  is  also  supplied  with  two 
commutators,  one  on  each  side  of  the  ring,  and  each  of  these 
serves  to  collect  half  of  the  sum  total  of  electricity  produced 
by  the  machine  ;  these  two  halves  can  be  connected  for  quan- 
tity or  for  tension,  according  to  the  exigencies  of  the  work  to 
be  done ;  or,  if  it  is  desirable,  one  current  may  be  used  to 
excite  the  field  magnets  and  the  other  for  the  working  current. 

OCTAGONAL  MACHINES. 

In  all  the  preceding  machines  there  are  only  the  two  field 
magnets  or  inducing  poles ;  only  two  currents  of  opposite 
direction  are  produced,  which,  united  in  the  external  circuit, 
furnish  only  a  single  current.  To  increase  the  power  of  his 
machines  in  the  proportions  which  the  applications  to  the 
transmission  of  power  necessitate,  M.  Gramme  has  increased 
the  dimensions  of  his  ring  so  as  to  exert  upon  it  the  influence 
of  four  electro-magnets  simultaneously.  The  four  successive 
poles  are  alternately  of  contrary  name,  and  the  commutations 
take  place  in  planes  passing  through  the  axis  of  rotation, 
but  forming  with  each  other  an  angle  of  ninety  degrees.  The 
ring  is  thus  divided  into  two  parts,  each  working  like  a  com- 
plete ring  of  the  ordinary  type.  Four  rubbers,  pressing  on  a 
single  commutator,  gather  the  two  currents,  produced  simul- 
taneously, which  can  be  connected  for  quantity  or  for  ten- 
sion. The  large  diameter  of  the  ring  makes  it  possible  to 
obtain,  with  a  moderate  speed  of  rotation,  a  more  rapid  move- 
ment of  the  helices  in  front  of  the  inducing  poles.  The  par- 
ticular form  of  the  structure  has  given  to  these  machines  the 
name  of  octagonal.  It  will  be  understood  that  this  system 
can  be  pushed  still  further,  enabling  us  to  construct  machines 
of  very  high  power. 

ALTERNATING-CURRENT  MACHINES. 

Nothing  remains  for  us  now,  to  complete  the  review  of  the 
numerous  inventions  of  M.  Gramme,  except  to  speak  of  his 
alternating-current  machines.  We  have  seen  that  on  account 
of  the  improvements  of  regulators,  several  lights  can  be  ob- 


THE  GRAMME   MACHINES.  249 

tained  from  one  machine,  provided  its  tension  is  in  proportion 
to  the  sum  of  the  resistances  of  the  exterior  circuit.  But  this 
tension  increases  rapidly  with  the  number  of  lights ;  it  re- 
quires, besides  the  increased  motive  power  necessary  for  its 
production,  much  greater  precautions  in  the  insulation  of  the 
wires  of  the  machine  and  of  the  conducting  or  line  wires ; 
thus,  at  first,  the  practical  number  of  lamps  was  limited  to 
four  or  five  per  circuit,  according  to  their  intensity.  With 
double-ring  machines  twelve  lights  on  one  circuit  were  at- 
tained. But  it  is  easy  to  increase  this,  if  currents  of  such  high 
tension  do  not  frighten  us ;  and  we  shall  see  further  on  that 
Mr.  Brush,  an  American,  as  might  have  been  expected,  made 
his  machines  produce  a  current  that  could  support  forty  lights 
on  a  circuit  ten  or  twelve  kilometres  long. 

This  is  the  only  possible  solution  with  direct-current  ma- 
chines, because  of  the  difficulty  of  multiplying  commutators  ; 
but  with  alternating  currents,  which  are  more  easily  collected, 
several  of  them  can  be  taken  from  the  same  machine,  each 
distinct  and  independent ;  thus  a  great  number  of  lights  is 
obtained  by  the  use  of  multiple  circuits ;  first,  a  division  of 
the  total  production  of  the  machine  into  several  currents,  and 
then  a  division  of  each  of  these  among  several  lamps.  We 
have  shown  how  alternating-current  machines,  with  movable 
field  magnets  and  fixed  armature  coils,  were  thus  reached, 
which  arrangement  Mr.  Holmes  patented  in  1857.  We  shall 
see  how  M.  Gramme  transformed  his  machine  in  1877  to  adapt 
it  to  the  Jablochkoff  candles. 

He  preserved  his  original  ring,  but,  making  it  stationary, 
he  could  increase  its  dimensions.  The  ring  became  a  cylinder, 
within  which  turns  an  inductor  formed  of  an  electro-magnet 
with  multiple  alternate  poles,  whose  arms  radiate  from  the 
axis  of  rotation,  and  whose  poles,  considerably  drawn  out, 
leave  only  a  small  intervening  space. 

The  wire  which  envelops  this  cylinder  is  divided  into  as 
many  sections  as  there  are  arms  to  the  field  magnet,  and  each 
section  contains  the  same  number  of  coils,  so  that  the  corre- 
sponding coils  of  each  of  these  sections  are  always  placed  in 
the  same  relation  to  the  poles  of  the  inductor.  The  currents 
which  are  thus  produced  at  the  same  instant  are  of  similar 
direction,  and  can  be  united.  The  diagram  (Fig.  156)  shows 
that  the  coils  a  a,  b  £,  c  <?,  d  d,  form  as  many  distinct  groups, 
each  furnishing  two  currents  of  opposite  direction,  due  to  the 


250 


PRODUCTION   OF  ELECTRIC  CURRENTS. 


approaching  to  and  departure  from  the  field-magnet  poles. 
This  annular  arrangement  of  the  armature  coils  is  advan- 
tageous, as  the  inductor  works  with  more  continuity,  and  be- 
cause, if  the  currents  of  different  groups  vary  in  intensity  on 
account  of  the  relative  position  which  each  of  them  occupies 

in  succession,  the  mini- 

x  ma  are  much  less  feeble 

than  in  other  systems, 
where  they  are  almost 
null  in  the  center  of 
the  comparatively  large 
space  intervening  be- 
tween the  armature  coils. 
By  using  two  rings, 
supplied  with  rubbers, 
the  exciting  current  pro- 
duced originally  by  a 
small  machine  with  con- 
tinuous current,  called 
the  exciter,  and  situated 
near  it,  can  be  passed 
into  the  rotating  field 

magnet.  This  arrangement  presents  several  inconveniences  : 
in  the  first  place,  it  increases  the  organs  of  transmission ; 
next,  as  the  magnetization  of  the  field  is  extremely  sensitive 
to  variations  in  the  exciting  current,  it  multiplies  the  chances 
of  irregularity  in  the  light. 


Fia.  156. — Diagram  of  alternating-current  Gramme 
machine. 


SELF-EXCITING  MACHINES. 

To  remedy  these  inconveniences,  M.  Gramme  modified  his 
exciter  so  as  to  make  it  possible  to  place  both  machines  in 
the  same  framework,  and  use  only  one  pulley  to  work  both 
at  the  same  time.  These  new  machines,  invented  in  1879, 
have  been  named  self -exciting  (auto-excitatrices\  (Pig.  157.) 

The  four  arms  of  the  inductor  of  the  exciter  are  attached 
radially  to  the  inner  side  of  a  ring,  fastened  to  one  of  the 
ends  of  the  frame,  and  cast  in  one  piece  with  it ;  their  like 
poles  are  thus  placed  opposite  each  other  in  the  apex  of  the 
two  angles  thus  formed.  The  armature  ring  is  fastened  on 
the  same  shaft  as  the  movable  inductor  of  the  alternating- 
current  machine,  which  is  not  otherwise  changed.  The  regu- 


THE   GRAMME  MACHINES. 


la  ting,  which  is  done  preliminarily  by  finding  the  best  speed 
for  the  exciter  when  separate,  is  here  obtained  by  means  of 
a  resistance  interposed  in  the  circuit  of  the  exciting  machine  ; 
by  making  this  resistance  vary,  the  intensity  of  the  current 
is  changed,  and  consequently  the  magnetism  of  the  field 
magnet  as  well  as  the  intensity  of  the  alternating  currents  is 
changed. 

The  most  usual  types  are  :  one  for  eight  candles  of  forty 
carcels,  or  twelve  candles  of  twenty-five  carcels ;  another  for 


024. 

SffilSi 


FIG.  157. — Self-exciting  alternating-current  Gramme  machine. 

sixteen  candles  of  thirty-five  carcels,  or  twenty-four  candles 
of  twenty  carcels.  A  machine,  with  separate  exciter,  has 
even  been  constructed  capable  of  supporting  sixty  candles  at 
once. 

We  will  only  speak  here,  as  a  reminder,  of  the  modifica- 
tions introduced  by  M.  Jamin  in  self-exciting  machines  ;  they 
have  principally  borne  upon  the  use  of  the  exciting  current, 
and  the  increase  of  tension  of  the  alternating  currents.  The 


252 


PRODUCTION  OF  ELECTRIC  CURRENTS. 


speed  of  the  machine  can  be  increased  by  them,  as  well  as  the 
expenditure  of  motive  power ;  the  increase  of  tension  has 
made  possible  the  lighting  a  number  of  lamps  in  the  same 


FIG.  158.— M.  Gramme. 

circuit,  but  their  light  "  diminished  because  the  heat  regener- 
ated in  each  of  them  is  less." 

This  last  expression  recalls  the  fact  that  the  heat  of  the 
voltaic  arc  is  the  result  of  that  which  is  set  free  by  the  burning 

^ combustible  under  the  boiler, 

or  by  the  gas  burned  in  the 
cylinder  of  the  gas-engine ; 
it  still  represents  heat,  even 
if  a  water-wheel  be  used,  be- 
cause it  is  the  heat  of  the  sun 
which  transforms  the  water 
into  vapor,  and  causes  it  to 
descend  in  the  form  of  rain 
to  supply  our  water-courses. 
All  our  sources  of  artificial 
heat  are  really  the  accumu- 
lated solar  heat  presented  to 
FIG.  159.— Armature  of  the  Wood  machine,  us  under  three  different  f  orms : 


THE  GRAMME  MACHINES. 


253 


coal  inclosed  for  centuries  in  the  depths  of  the  earth ;  forests 
which  slowly  grow  under  our  eyes  ;  and,  finally  the  reservoirs 
of  motive  power,  and  consequently  of  the  heat  which  the 
movement  of  water  on  the  face  of  the  earth  create.  When 
we  shall  have  exhausted  the  first  resource,  which  we  waste, 
if  the  second  does  not  de- 
velop with  sufficient  rap- 
idity for  our  needs,  it  will 
be  electricity  that  will  en- 
able us  to  utilize  the  last. 
[The  Gramme  machine, 
as  made  in  this  country 
by  the  Fuller  Electrical 
Company,  after  the  de- 
signs of  Mr.  J.  J.  Wood, 
has  several  points  of  im- 
provement in  its  construc- 
tion. In  the  foreign  ma- 
chine the  central  portion 
surrounded  by  the  arma- 
ture ring  is  formed  of  a 
wooden  block,  driven  into 
position,  which  operation 
not  infrequently  disar- 
ranges the  wire  and  in- 
jures the  insulation.  It, 
moreover,  prevents  the  cir- 
culation of  air,  which  is 
useful  in  keeping  the  arm- 
ature cool.  In  the  Amer- 
ican machine  the  armature 
ring  is  mounted  upon  a 
gun-metal  frame,  consist- 
ing of  a  central  hub  and 
radial  bars  or  spokes.  In 
its  revolution  this  arma- 
ture has  a  fan-like  action, 
and  the  wire  is  consequent- 
ly kept  cool.  This  construction  is  clearly  shown  in  Figs.  159 
and  160.  The  general  appearance  of  the  machine,  which  does 
not  differ  greatly  from  the  foreign  form,  is  shown  in  Fig.  161. 
The  regulation  of  the  machine,  in  accordance  with  the  num- 


254: 


PRODUCTION  OF  ELECTRIC   CURRENTS. 


ber  of  arc-lamps  in  circuit,  is  effected  by  moving  the  brushes 
to  or  from  the  maximum  position.     This  is  done  by  the 


attendant  when  the  necessity  for  it  is  shown  by  an  electro- 
magnetic indicator.] 


THE   GRAMME  MACHINES.  255 


PRECURSORS  OP  GRAMME. 

As  is  often  the  case  with  important  discoveries,  M. 
Gramme's  labors  had  been,  unknown  to  him,  preceded  by 
analogous  studies,  carried  on  in  1860  by  an  Italian  student, 
M.  Pacinotti,  to-day  professor  at  the  University  of  Cagliari. 

The  original  model  of  this  inventor  (Fig.  162),  which  was 
shown  at  the  International  Electrical  Exhibition  at  Paris  in 
1881,  present  so  surprising  a  resemblance  to  M.  Gramme's 
machine,  that  we  are  obliged  to  ask  why  M.  Pacinotti' s  ma- 
chine remained  completely  forgotten  until  the  extraordinary 
success  of  M.  Gramme's  machines  made  known  its  value.  It 
is  without  doubt  because,  at  the  time  when  the  learned  Italian 
made  his  researches,  the  principal  direction  of  such  work  was 
to  produce  motive  power  by  means  of  electricity,  and  his  ap- 
paratus was  intended  to  be  an  electro-motor  ;  under  this  form 
they  were  necessarily  doomed  to  impotence  as  long  as  they 
were  obliged  to  use  batteries  for  the  production  of  the  elec- 
tricity. 

Furthermore,  the  inventor,  then  only  a  student,  was  very 
soon  engaged  as  assistant  to  Donati  in  the  Astronomical  Ob- 
servatory of  Florence,  and  obliged,  by  the  requirements  of 
this  position,  to  direct  his  attention  to  other  studies. 

M.  Pacinotti  shows  clearly,  in  the  description  of  his  ma- 
chines, published  in  1864  by  a  scientific  Italian  journal,  "II 
Nuovo  Cimento,"  that  it  was  doubtless  possible  to  transform 
his  electro-motor  into  an  electro-magnetic  generator  of  contin- 
uous currents  ;  but  he  did  not  appreciate  the  vast  importance 
of  this  transformation,  and,  the  circumstances  not  tending  in 
such  a  direction,  he  gave  up  his  experiments  on  the  subject. 
We  must  add  here  that  the  jury  of  the  Exhibition  has  recog- 
nized the  merit  of  M.  Pacinotti's  inventions,  and  has  decreed 
him,  at  the  same  time  with  M.  Gramme,  the  highest  award  at 
its  disposal,  the  diploma  of  honor. 

In  M.  Pacinotti's  machine  the  field  magnet  is  an  electro- 
magnet, whose  poles  spread  out  into  the  arc  of  a  circle,  within 
which  the  armature  ring  rotates,  which  the  inventor  calls  the 
transversal  electro-magnet ;  it  is  a  ring  of  iron  provided  with 
exterior  projections,  between  which  the  coils  of  copper  wire 
are  wound.  These  coils  are  all  wound  the  same  way,  and  the 
ends  of  the  wires  are  soldered  to  as  many  pieces  of  copper  im- 
bedded in  a  wooden  drum,  which  form  a  commutator,  against 

18 


PRODUCTION  OF  ELECTRIC  CURRENTS. 


which  two  metallic  rubbers  press  ;  the  passage  of  the  current 
through  the  coils  magnetizes  the  annular  iron  ring,  which  can 
be  considered,  in  the  words  of  M.  Pacinotti,  as  formed  of  two 
semicircular  magnets  connected  by  their  similar  poles.  The 
magnetic  poles  of  the  ring  being  attracted  and  repelled  by  those 
of  the  fixed  electro-magnet,  the  ring  acquires  a  movement  of 
rotation.  The  same  current  circulates  successively  in  the  wire 
of  the  ring  and  in  the  magnetizing  coils  of  the  field  magnets. 

By  showing  how  his  motor  could  be  transformed  into  a 
generator  of  electricity,  M.  Pacinotti  explains  the  method  of 
producing  currents  of  the  same  direction  and  the  rules  to  be 


Fig.  162.— Original  model  of  the  Pancinotti  machine,  exhibited  at  the  Exposition  of  Elec- 
tricity at  Paris,  1881. 

followed  in  placing  the  rubbers  in  position.  Here  was  the 
germ,  as  early  as  1860,  of  all  that  constitutes  the  best  actual 
machines  ;  and  we  should  add,  furthermore,  that  M.  Pacinotti 
himself  had  been  preceded  eight  years  by  an  American  sa- 
vant, Mr.  Page,  well  known  among  electricians.  In  1852  Mr. 
Page  had  constructed  in  Washington  a  motor,  with  circular 
electro-magnets,  with  which  he  succeeded  in  driving  a  small 
locomotive.  ( 

Among  the  predecessors,  not  yet  generally  known,  of  the 
Gramme  machine,  we  must  cite  the  one  patented  and  con- 


THE  SIEMENS  MACHINES.  257 

structed  in  1866  by  M.  Worms  de  Romilly,  on  a  theory  far 
different  from  that  which  guided  M.  Gramme.  He  also  wound 
his  sectional  bobbins  in  reverse  directions,  which  forced  him 
to  redirect  the  currents.  We  have  already  explained  that 
this  redirection  was  impracticable. 

The  Electrical  Exhibition  in  Paris  has  also  shown  us  a 
model  of  much  older  date,  as  it  goes  back  to  1842.  It  is  a 
motor  invented  by  M.  Elias,  which  was  exhibited  in  the  Dutch 
section.  All  the  elements  of  modern  machines  are  found  here 
in  principle— windings,  commutation,  etc. ;  all  this,  it  is  true, 
in  the  function  of  motor,  as  with  M.  Pacinotti.  Thus  a  quarter 
of  a  century  was  lost,  because  the  question  had  been  wrongly 
put,  and  because  the  world  had  never  dreamed  of  perfecting 
the  apparatus  for  production  before  the  one  destined  to  util- 
ize the  current. 


CHAPTER  VII. 

THE  SIEMENS  MACHINES. 

THE  two  firms  of  Messrs.  Siemens  Brothers  and  Siemens 
and  Halske  use  for  their  actual  lighting  two  types  of  ma- 
chines, whose  construction  is  due  to  M.  Heffner  von  Alteneck : 
one  is  of  the  continuous-current  type  and  dates  back  to  1872  ; 
the  other,  of  alternate  currents,  dates  from  1878.  We  shall 
study  both  at  once,  for  they  generally  work  together,  one 
serving  as  exciter  for  the  other. 

The  continuous-current  machine  (Fig.  163)  has  for  a  field 
two  electro-magnets  with  consequent  poles ;  these  poles,  in- 
stead of  being  massive  like  those  of  M.  Gramme,  are  formed 
of  bars  of  soft  iron,  bent  in  the  arc  of  a  circle,  and  arranged 
one  alongside  of  the  other  without  touching,  so  that  air  cir- 
culates in  the  intervals,  and  contributes  to  the  prevention  of 
the  heating  of  the  machine. 

The  secondary  coil  or  armature  differs  essentially  from  that 
of  M.  Gramme  ;  it  is  a  cylinder  of  iron,  which  is  nearly  three 
times  as  long  as  its  diameter ;  the  copper  wire  is  wound  ex- 
clusively around  this  cylinder,  parallel  to  the  axis  of  rota- 
tion ;  it  does  not  return  through  the  interior.  It  is,  then,  the 
branches  diametrically  opposed  to  each  other  of  one  and  the 


258  PRODUCTION  OF  ELECTRIC   CURRENTS. 

same  helix,  which,  are  simultaneously  subjected  to  induction, 
while  in  the  ring  of  M.  Gramme  it  is  the  two  helices  situated  at 
the  extremities  of  the  same  diameter  which  are  subjected  at 
the  same  time  to  the  action  of  the  field  magnets ;  it  follows 
that  in  the  latter  system  it  is  the  wires  situated  in  the  interior 
of  the  ring  that  can  be  considered  inactive,  if  it  be  admitted 
that  the  iron  core  serves  as  a  sort  of  magnetic  screen  ;  in  the 
drum  of  Heffner  von  Alteneck  it  is  the  portion  of  the  wires 
which  cross  each  other  on  the  extremities  of  the  cylinder  that 
are  inactive.  It  can  be  deduced,  then,  that,  under  equal 


FIG.  163. — Siemens  continuous-current  machine — vertical  model. 

conditions,  the  superiority  of  one  system  over  the  other  can 
be  estimated  from  the  relative  proportion  of  the  active  to  the 
inactive  wire. 

To  construct  this  drum  wooden  disks,  which  constitute  a 
primary  core,  are  arranged  on  the  shaft  of  the  machine,  one 
beside  the  other,  on  which  several  layers  of  annealed  iron 
wire  are  circularly  wound.  This  first  envelope  is  designed 
to  charge  the  magnetic  field  of  the  inducing  poles.  The  drum 
thus  formed  is  covered  again  with  taffeta,  varnished  with  an 
insulating  compound,  and  it  is  terminated  by  winding  the 


260 


PRODUCTION   OF  ELECTRIC   CURRENTS. 


copper  wire  longitudinally,  as  has  been  said  above.  This  wire 
is  divided  into  an  equal  number  of  bundles,  or  coils,  placed 
one  beside  the  other,  and  connected  by  their  inlet  and  outlet 
wires ;  the  whole  forms  an  endless  circuit,  which  can  be  un- 
derstood from  an  inspection  of  the  characters  of  Fig.  165,  in 
which  the  coils  are  supposed  to  be  reduced  each  one  to  a 
single  wire. 

The  junctions  of  the  coils  are  connected  to  plates  of  a  com- 
mutator analogous  to  that  of  M.  Gramme,  and  fastened  upon 
the  same  shaft  as  the  drum.  Fig.  166  shows  the  diagram  of 
these  connections ;  it  will  be  seen  that  they  are  so  arranged 
that  the  total  circuit  of  the  coils  is  always  divided  into  two 
halves,  in  which  the  currents  go  in  opposite  directions  and 
unite  at  the  two  diametrically  opposite  plates  of  the  commu- 
tator. 

Thus  from  c  to  g  and  from  g  to  c  the  circuits  are  : 
c55'    dllf    eV\    f4'4    g 

h  +          +  '       + 

c  3  3'    b  2'  2    a  8  8'    li§®    g 

+  +  +  + 

If  the  drum  and  the  commutator,  whose  movements  coin- 
cide, continue  to  turn  in  the  direction  of  the  arrow,  it  is  the 
plates  b  and  f  which  come  opposite  the  rubbers,  and  the  cir- 
cuits become : 

533'    c55'    dir    e\'\   f 

+          +  +   •     + 

b22f    a  8  8'    7i  6  &    $44'    f 

+  +  +         + 

These  machines  are  built  of  two  types,  that  only  differ 
in  the  position  of  the  field  magnets,  which  are  sometimes 
placed  vertically  and  sometimes  horizontally.  They  serve  not 
only  as  exciters  for  alternate-current  machines,  but  are  also 
employed  for  the  production  of  the  more  intense  of  the  elec- 
tric lights,  such  as  those  of  light- house,  war,  and  marine  ap- 
paratus. There  are  four  models,  designated  by  the  letter  D, 
whose  respective  conditions  are  as  follows  : 


MACHINES. 

Horse-power. 

D2. 

34. 

D8  

2A 

D8.. 

2 

Number  of  revolutions  per 
minute. 

650 

850 

1,100 


Light  produced  in  carcels. 


From  660  to  850 
300 
200 


THE  SIEMENS   MACHINES. 


261 


\      r 


FIG.  165. — Diagram  of  the  winding  of  the  Heffner  von 
Alteneck  drum. 


The  machine  D5  is  a  very  small  machine,  which  makes 
about  1,300  revolutions,  and  is  only  employed  as  exciter. 

The  alternating-current  machines  of  Mr.  Siemens  have  one 
peculiarity  which  must  not  be  passed  over  ;  the  iron  cores  of 
the  armature  are  entirely  suppressed,  and  the  only  induction 
utilized  is  that  which 
is  produced  directly 
in  the  wires  compos- 
ing it  (Fig.  167).   The 
moving  part  is  light- 
er, and  the  principal 
cause  of  heating  is 
done  away  with. 

The  inductors  are 
straight  electro-mag- 
nets, divided  into 

two  parallel  series  placed  facing  each  other ;  they  are  fastened 
in  a  circle  on  the  inner  sides  of  two  cast-iron  frames  bolted 
vertically  on  a  cast-iron  base  and  solidly  cross-braced ;  the 
cores  terminate  in  polar  plates,  formed  into  sectors.  The 
consecutive  poles  of  each  series  are  of  opposite  polarity,  and 

unlike  poles  are  placed  op- 
posite each  other.  All  the 
magnetizing  coils  of  these 
electro-magnets  are  wound 
in  the  same  direction,  and 
it  is  by  changing,  by  the 
way  of  fastening  the  inlet 
and  outlet  wires,  the  direc- 
tion of  current  traversing 
them  that  their  polarities 
are  reversed. 

The  armature  is  com- 
posed of  non-magnetic  bob- 
bins, whose  wires  are  wound 
around  wooden  cores,  fast- 
ened between  copper  disks ;  holes  pierced  in  these  permit 
the  air  to  carry  off  the  small  amount  of  heat  which  can  be 
developed  in  the  wires.  These  bobbins  are  equally  elongated 
in  the  form  of  sectors,  and  are  fastened  by  their  disks  around 
a  bronze  wheel ;  the  whole  arrangement  presents  the  appear- 
ance of  a  flat  disk,  which  rotates  between  the  two  circles  of 


FIG.  166. — Diagram  ot  the  connection  of  the  coils. 


262  PRODUCTION   OF  ELECTRIC  CURRENTS. 

inductors,  or  field  magnets,  whose  influence  it  receives  later- 
ally, while  the  preceding  systems  are  influenced  cylindrically. 
The  central  part  of  the  brass  wheel  is  supplied  with  a 
wooden  disk  to  which  the  wires  from  the  bobbins  are  attached, 
either  directly  together  or  by  means  of  friction-rings.  The 
armature  bobbins  are  connected  either  in  tension  or  in  quan- 
tity, as  may  be  required  ;  they  form  thus  one  or  more  series 
whose  currents  are  separately  collected;  each  of  these  cur- 
rents leaves  the  machine  by  a  special  ring ;  but  all  return  to  a 
common  ring,  a  little  larger  than  the  others. 


FIG.  167. — Alternating-current  machine  of  Heffner  von  Alteneck. 

There  are  three  types  of  these  machines,  designated  by  the 
letter  W,  having  the  capacity  of  supplying  one,  two,  or  four 
circuits. 

W1,  with  16  bobbins,  running  at  the  rate  of  500  revolutions 
per  minute,  and  of  sufficient  capacity  to  supply  16  to  32  of 
Siemens' s  differential  lamps,  with  the  machine  D6  as  exciter. 

W2,  with  12  bobbins,  making  600  revolutions,  and  of  capa- 
city to  supply  12,  16,  and  20  lamps,  with  the  machine  D6  as 
exciter. 

W8,  with  8  bobbins,  making  700  revolutions,  and  of  capa- 


THE   SIEMENS   MACHINES.  263 

city  to  supply  4,  6,  8,  or  10  lamps,  with  the  machine  D5  as 
exciter. 

M.  Heffner  von  Alteneck  has  succeeded,  by  several  very 
ingenious  modifications,  in  transforming  this  alternate-current 
machine  into  a  continuous  current,  one  which  only  contains 
one  commutator  and  two  brushes,  whatever  be  the  number  of 
field  magnets.  This  opens  a  new  way  for  the  construction  of 
generators  yet  more  powerful  than  the  machines  with  four 
field  magnets  already  existing,  such  as  the  octagonal  machine 
of  M.  Gramme,  of  which  we  have  already  spoken,  and  the 
magneto-electric  machine  of  the  same  kind  constructed  by  M. 
de  Meritens,  a  machine  which  we  shall  examine  further  on. 

Here  we  shall  not  enter  upon  this  very  interesting  study, 
one  that  at  the  same  time  is  very  complicated ;  we  refer  to 
the  study  of  the  course  of  the  currents  in  this  class  of  ma- 
chine, and  the  method  of  collecting  them  ;  such  of  our  readers 


FIG.  168. — Diagram  of  armature  and  field  coils  of  Ferranti  machine. 

as  are  interested  in  these  special  questions  will  find  them 
treated  in  the  review  of  the  machines  of  the  Paris  Electrical 
Exhibition,  published  by  uThe  Genie  Civil"  (November  1, 
1881). 

•  [An  alternating-current  machine,  of  the  same  general  ap- 
pearance as  the  Siemens,  but  which  differs  materially  from  it 
in  the  construction  of  its  armature,  has  been  designed  by  Sir 
William  Thomson  and  M.  Ferranti.  The  field,  like  the  Sie- 
mens, consists  of  two  circular  sets  of  bobbins  with  iron  cores, 
between  which  the  armature  revolves.  The  armature  wire, 
instead  of  being  wound  in  coils,  however,  is  in  the  form  of  a 
zigzag,  as  shown  in  Fig.  168  by  the  dark  band.  One  end  of 
this  is  attached  to  a  ring  on  the  axle,  and  the  other  to  a  simi- 
lar ring  insulated  from  both,  and  the  current  is  taken  off  by 
two  rubbers  bearing  upon  the  rings.  The  field  magnets  are 


264 


PRODUCTION   OF  ELECTRIC   CURRENTS. 


excited  by  a  separate  continuous-current  machine.  An  arma- 
ture of  this  form  has  the  advantages  of  little  liability  of  over- 
heating and  low  cost  of  manufacture. 

The  largest  dynamo  which  has  yet  been  constructed  is  an 
alternating-current  one  designed  by  Mr.  J.  E.  H.  Gordon,  and 
shown  in  Fig.  169.  It  consists  essentially  of  a  central  disk 
carrying  electro-magnets,  and  revolving  between  sets  of  simi- 
lar electro-magnets  on  each  side  of  it.  The  rotating  portion 
is  the  field,  and  the  stationary  electro-magnets  the  armature. 


FIG.  169. — Gordon  alternating-current  dynamo. 

This  latter  contains  128  coils,  64  on  each  side,  this  being  twice 
as  many  as  in  the  rotating  part.  The  coils  of  the  revolving 
magnets  are  excited  by  a  separate  continuous- current  ma- 
chine, as  is  the  field  of  the  Ferranti.  The  machine  has  a  total 
weight  of  eighteen  tons,  that  of  the  revolving  part  being  seven 
tons.  Its  diameter  is  eight  feet  nine  inches,  and  it  is  de- 
signed, when  the  machine  is  giving  its  maximum  current,  to 
be  driven  at  200  revolutions  per  minute,  and  supply  7,000  six- 
teen-candle  incandescent  lamps.] 


266  PRODUCTION  OF   ELECTRIC  CURRENTS. 

CHAPTER  VIII. 

REGENT  DYNAMO-ELECTRIC  MACHINES. 

THE  systems  of  Messrs.  Siemens  and  M.  Gramme  have 
given  rise  to  two  or  three  others  of  the  same  kind,  whose 
inventors  were  content  to  combine  in  different  ways  organs 
and  parts  borrowed  from  the  preceding  machines,  with  slight 
modifications.  The  machines  of  Mr.  Weston  and  Mr.  Maxim, 
and  even  that  of  Mr.  Edison,  are  of  this  number. 

I.  WESTON  MACHINE. 

Mr.  Weston  had  exhibited  in  Paris,  in  1878,  a  dynamo- 
electric  machine  constructed  for  electro-plating,  which  does 
not  concern  us  ;  it  was,  moreover,  described  in  1879,  in  the 
journal  "La  Lumiere  Blectrique."  We  shall  only  examine 
the  new  continuous-current  machine. 

As  Fig.  170  shows,  this  machine  resembles  in  the  form 
of  its  field  magnets  the  machine  of  M.  Gramme,  and  in  its 
form  of  armature  the  machine  of  Mr.  Siemens  ;  it  only  differs 


FIG.  171. — Weston  armature. 

from  these  in  some  details.  Thus  the  poles  of  the  field  mag- 
nets are  divided  by  open  slots,  designed  to  prevent  the  pro- 
duction of  Foucault  currents,  and  to  facilitate  the  circulation 
of  air.  The  slots  thus  cut  out  are  shorter  in  the  middle  than 
at  the  extremities,  which,  according  to  the  inventor,  insures 
more  regularity  in  the  production  of  the  currents. 

[The  armature,  wound  with  its  wire,  is  shown  in  Fig.  171, 
and  the  core  in  Fig.  172.  This  latter  is  composed  of  a  num- 
ber of  toothed  disks  of  sheet-iron  (Fig.  173),  which  are  strung 
on  the  shaft  and  separated  from  each  other  by  insulating 
washers.  These  disks  and  the  washers  are  perforated  to 


RECENT   DYNAMO-ELECTRIC  MACHINES. 


267 


allow  the  circulation  of  air.  The  wire  is  wound  lengthwise  in 
the  grooves  between  the  projecting  teeth.  The  commutator  is 
clearly  shown  in  Fig.  170.  The  plates  were  formerly  arranged 
spirally,  but  they  are  now  constructed  like  those  of  the 
Gramme  and  other  machines.  The  brushes  are  formed  of  a 


FIG.  172.— Core  of  Weston  armature. 

number  of  strips  of  sheet-copper,  and  are  mounted  in  such  a 
manner  that  their  position  on  the  commutator  can  be  readily 
charged  by  means  of  the  handle  shown.  The  field  magnets 
are  placed  in  a  shunt  circuit  in  both  the  arc  and  incandescent 
machine.] 

At  the  Palais  de  1' Industrie  two  Weston  machines  sup- 
plied eighteen  lamps  of  the  same  inventor  with  an  expendi- 
ture of  eighteen  horse-power. 


II.  MAXIM  MACHINE. 

Hiram  S.  Maxim's  machine  presents  the  reverse  combina- 
tion of  the  one  just  described  ;  the  field  magnets  are  identical 
with  those  of  the  Siemens  continuous-cur- 
rent machines,  and  the  armature  is  a  Paci- 
notti  and  Gramme  ring  a  little  elongated ; 
but  what  is  most  interesting  is  the  general 
arrangement  adopted  to  obtain  with  these 
machines  a  combination  suited  for  lighting 
by  incandescence,  and  the  current-regulator, 
invented  by  Mr.  Maxim  to  maintain  the  pro- 
duction of  a  lighting  current  in  exact  pro- 
portion to  the  demand  made  upon  it.     It 
forms,  with  the  lamp  of  the  same  inventor, 
a  complete  system  in  which  all  the  conditions  of  the  problem 
seem  fulfilled,  and  which  it  appears  has  successfully  worked 
for  some  time  in  New  York. 

This  system  comprises  one  or  more  machines  for  supply- 


Fio.  173.  —  Toothed 
iron  disk  used  in 
Weston  armature. 


268 


PRODUCTION  OF  ELECTRIC   CURRENTS. 


ing  the  lamps,  and  an  exciting-machine  for  supplying  the 
field  magnets  of  the  first-named. 

It  is  to  the  exciting-machine  that  the  regulator  is  adapted — 
by  the  aid  of  which  the  current  supplying  the  lamps  auto- 


matically regulates  the  intensity  of  the  exciting  current — in 
consequence,  it  (the  lighting  current)  increases  or  diminishes, 
according  to  necessity,  the  power  of  the  field  magnets  which 
produce  it. 


RECENT   DYNAMO-ELECTRIC  MACHINES. 

The  elements  of  the  two  machines  are  the  same :  the  field 
magnets  are,  as  we  have  said,  electro-magnets  identical  with 
those  of  Mr.  Siemens.  The  annular  armature  is  arranged  like 
Pacinotti's  ring  and  Weston's  drum  ;  it  is  formed  of  a  series 
of  sheet-iron  washers,  cut  out  by  means  of  a  die,  with  fifteen 
projections  distributed  on  their  exterior  circumference.  A 
sufficient  number  of  these  washers  are  placed  together,  sepa- 
rated by  sheets  of  paper,  so  as  to  form  a  hollow  cylinder 
whose  interior  surface  is  smooth,  and  whose  exterior  surface 
has  fifteen  longitudinal  projections  or  ribs,  between  which  the 
wire  is  wound.  The  wire  is  wound  transversely  (longitudi- 
nally along  the  outside  and  inside  of  the  cylinder,  as  in  the 
Gramme  ring),  and  is  divided  into  sections  whose  incoming 
and  outgoing  ends  are  fastened,  two  by  two,  to  the  plates  of 
a  commutator  analogous  to  that  of  M.  Gramme.  The  brushes 
are  double,  and  one  is  longer  than  the  other,  so  that  there  is 
always  one  at  least  in  contact  with  the  plates  of  the  com- 
mutator. This  arrangement  had  already  been  adopted  by  Mr. 
Siemens.  The  openings  which  the  ribs  of  the  ring  form  be- 
tween the  wires,  have  for  object,  as  in  Weston's  drum,  the 
facilitating  the  cooling  by  the  circulation  of  air  caused  by  the 
rotation. 

In  the  large  machines  which  supply  lamps  (Fig.  174),  the 
armature  ring  is  doubled,  of  which  we  have  seen  an  example 
in  certain  machines  of  M.  Gramme.  The  coils  of  wire  are 
wound  half  to  the  right  and  half  to  the  left,  and  connected  to 
two  commutators  placed  at  each  end.  The  two  currents  thus 
collected  can  be  used  separately  ;  but  for  incandescent  lamps 
they  are  preferably  connected  in  quantity,  a  single  circuit 
only  being  formed,  on  which  the  lamps  are  placed  in  multiple 
arc.  Again,  mixed  lighting  can  be  done,  half  of  the  ring 
being  used  for  incandescent  lamps,  and  the  other  half  for 
one  or  two  voltaic-arc  regulators.  All  these  groupings  are 
made  very  easily  by  means  of  a  plug  commutator,  shown  on 
the  top  of  the  machine. 

The  exciting-machine  (Figs.  175,  176)  is  generally  less  pow- 
erful ;  the  ring  is  not  duplex,  and  there  is  only  one  commu- 
tator with  one  pair  of  brushes ;  but  the  plates  of  this  commu- 
tator are  brought  together,  two  and  two,  at  their  ends,  so  as 
to  form  a  series  of  very  prolonged  Vs.  This  differs  a  little 
from  the  arrangement  in  helices  of  the  commutator  plates  of 
Mr.  Weston,  but  leads  to  the  same  result. 


270 


PRODUCTION   OF  ELECTRIC  CURRENTS. 


The  field  magnets  of  the  exciting-machine  are  placed  in 
the  same  circuit  as  those  of  the  lighting-machine,  and  a  single 
exciter  is  enough  for  several  machines.  It  is  on  this  field- 
magnet  circuit  that  Mr.  Maxim's  regulator  acts.  To  under- 


FIG.  175. — Maxim  exciting-machine  with  automatic  current  regulator.     Front  view. 


KECENT  DYNAMO-ELECTEIO  MACHINES. 


271 


stand  its  mechanism  it  must 
be  remembered  that  the  in- 
tensity of  the  lighting  cur- 
rent is  proportional  to  the 
power  of  the  field  magnets, 
and  that  this  depends  in  its 
turn  on  the  intensity  of  the 
exciting  current,  and  that,  if 
this  last  is  made  to  vary,  the 
two  other  elements  are  at  the 
same  time  modified. 

To  vary,  according  to  the 
needs  of  the  case,  the  inten- 
sity of  the  exciting  current, 
Mr.  Maxim  had  recourse  to 
displacing  the  brushes  on  the 
commutator;  we  have  seen 
that  the  currents  are  com- 
pletely collected  when  the 
brushes  are  placed  so  that 
the  two  halves  of  the  arm- 
ature contain  each  one  an 
equal  number  of  helices, 
traversed  by  the  currents  in 
the  same  direction,  only  op- 
posed one  half  to  the  other. 
If  the  brushes  are  removed 
from  this  position  the  cur- 
rent which  they  collect  di- 
minishes, because  each  of  the 
two  halves  of  the  armature 
contains  at  the  same  time 
helices  traversed  by  currents 
of  opposite  direction,  which 
neutralize  each  other  in  part, 
and  whose  difference  or  ex- 
cess alone  is  collected.  If 
the  displacement  is  carried 
out  until  an  angle  of  ninety 
degrees  is  reached,  the  hel- 
ices traversed  by  the  currents 
of  opposite  direction  will  be 

19 


FIG.  176. — Maxim  exciting-machine  with  cur- 
rent regulator.     Side  view. 


272  PRODUCTION  OF  ELECTRIC  CURRENTS. 

divided  into  equal  numbers  in  each  of  the  halves  of  the  ring  ; 
the  neutralization  will  be  complete,  and  no  current  will  be 
collected.  Thus  the  displacement  of  the  armature  brushes 
can  reduce  the  exciting  current  from  its  maximum  to  zero ; 
at  the  same  time  it  governs  the  power  of  the  field,  and  in 
consequence  the  production  of  the  lighting  current. 

The  brushes  are  mounted  on  an  independent  support, 
which  can  receive  a  rotary  movement  by  the  action  of  a 
toothed  sector  and  a  series  of  cog-wheels,  which  is  shown 
at  the  right  of  the  first  figure ;  the  system  comprises  two 
ratchet-wheels,  placed  vertically  one  over  the  other.  These 
wheels  can  be  actuated  by  a  horizontal  lever,  to  which  the 
main  shaft  of  the  machine  communicates,  by  light  gearing,  an 
oscillatory  movement.  This  lever  has  on  both  faces  a  small 
tooth,  by  which  it  turns  one  or  the  other  of  the  two  ratchet- 
wheels,  according  to  whether  it  is  raised  or  lowered ;  but 
when  it  is  horizontal,  the  separation  between  the  two  wheels 
lets  it  pass  freely. 

The  magnetic  part  of  the  regulator  comprises  two  dis- 
tinct electro-magnets,  having  each  one  different  and  succes- 
sive functions,  the  second  only  acting  as  a  safety  apparatus, 
if  the  first  is  insufficient,  and  to  give  it  time  for  acting. 
Both  are  wound  with  fine  wire,  forming  shunts  to  the  lamp 
circuit ;  the  second  has  a  slightly  greater  resistance. 

The  horizontal  lever  is  connected  with  the  armature  of  the 
first  electro-magnet ;  an  opposing  spring,  regulated  by  hand, 
pulls  this  armature,  whose  course  is  limited  by  two  abutting 
screws.  When  one  or  more  lamps  are  extinguished,  the  cur- 
rent becomes  too  intense  for  the  lamps  that  remain  ;  but  now 
the  derived  current  increases,  the  electro-magnet  attracts  its 
armature,  the  lever  drops  down,  and  one  of  its  teeth  engages 
with  the  lower  ratchet-wheel.  The  oscillatory  movement  of 
the  lever  determines  the  rotation  of  the  system,  and  conse- 
quently that  of  the  brush- carriers.  These  approach  the  neu- 
tral point ;  the  exciting  current  diminishes,  which  diminution 
is  followed  by  all  the  consequences  we  have  already  indicated. 
This  displacement  of  the  brushes  continues  to  be  effected  as 
long  as  the  lighting  current  has  not  attained  the  degree  of  in- 
tensity corresponding  to  the  number  of  lamps  in  use  ;  at  this 
moment  of  equilibrium  the  derived  circuit  grows  weaker,  the 
electro-magnet  relaxes  a  little  its  attraction  for  its  armature, 
and  the  toothed  lever  takes  the  horizontal  position  ;  the  ratch- 


RECENT  DYNAMO-ELECTRIC  MACHINES.  273 

et-wheels  remain  motionless.  If  new  lamps  are  lighted  again, 
the  current  in  the  shunt  circuit  grows  still  weaker  ;  the  oppos- 
ing spring  draws  the  armature  entirely  away,  and  lifts  up 
completely  the  toothed  lever,  which  acts  then  upon  the  upper 
ratchet-wheel.  A  reverse  movement  of  the  brushes  is  the 
result,  which  approach  the  points  where  the  current  collected 
will  attain  its  maximum.  The  power  of  the  field  magnets 
is  increased,  and  the  intensity  of  the  lighting  current  again 
becomes  of  the  necessary  strength. 

It  will  be  seen  that  the  whole  regulation  depends  upon  the 
opposing  spring,  and  that  it  suflices,  to  increase  or  diminish 
its  tension,  to  raise  or  lower  the  intensity  of  all  the  lamps ; 
they  can  be  reduced  to  simple  tapers. 

To  insure  the  absolute  regularity  of  the  light,  the  regulator 
must  be  made  very  sensitive ;  from  this  the  inconvenience 
follows  that  it  acts  very  slowly,  so  that  if  a  large  number  of 
lamps  are  suddenly  extinguished  the  intensity  of  the  current 
does  not  diminish  rapidly  enough  for  the  preservation  of  the 
remaining  lamps ;  here  the  second  electro-magnet  plays  its 
part,  being  excited  by  the  considerable  increase  in  the  derived 
current.  It  acts  by  placing  the  two  brushes  in  communica- 
tion by  a  cross  circuit  of  no  resistance  ;  the  field  magnets 
receive  no  longer  any  exciting  current,  and  in  consequence 
the  lighting  current  immediately  weakens ;  sometimes  even 
all  the  lamps  go  out,  which  is  an  excess  in  the  way  of  preser- 
vation which  must  be  avoided.  The  weakening,  however,  is 
only  of  very  short  duration,  because  the  derived  current  ceases 
at  the  same  time,  and  all  the  armatures  of  the  electro-magnets 
take  again  immediately  their  respective  positions. 

This  system  of  regulating  is  very  ingenious,  although  com- 
plicated ;  it  appeared  to  have  worked  very  well  in  America 
and  in  England ;  there  was  no  way  of  trying  it  at  the  Paris 
Exhibition,  doubtless  on  account  of  the  conditions  of  the  in- 
stallation.* 

III.  EDISON  MACHINE. 

[The  Edison  machine  is  of  the  Siemens  continuous-current 
type,  though  it  differs  from  it  in  constructive  details.  Being 
designed  to  work  on  a  circuit  of  low  resistance,  it  was  neces- 

*  [This  method  of  regulation  has  heen  abandoned  in  this  country  by  the  com- 
pany using  the  Maxim  incandescent  lamp,  in  favor  of  a  special  winding  of  the 
machine  supplying  the  lamp  circuit,  described  in  the  next  book.] 


FIG.  177.—  Edison  machine. 


RECENT  DYNAMO-ELECTRIC   MACHINES. 


275' 


sary  to  make  the  resistance  of  the  armature  as  small  as  pos- 
sible, and,  to  do  this  and  yet  get  sufficient  electro-motive 
force,  Mr.  Edison  sought  to  make  the  magnetic  field  of  great 
strength.  To  this  end  he  has  constructed  his  field  magnets 
much  more  massive  than  those  of  other  machines,  and  has 
greatly  increased  the  length  of  the  cores  and  the  wire  wound 
on  them.  In  the  smaller  machines  these  cores  are  usually 
placed  upright,  but  in  the  large  steam  dynamos  used  at  cen- 
tral stations  they  are  arranged  horizontally.  Fig.  177  shows  a 
machine  of  the  former  kind,  and  the  large  central  station  ma- 


FIG.  178. — Edison  steam  dynamo. 

chine  such  as  is  being  used  in  the  first  district  in  New  York, 
and  on  the  Holborn  Viaduct,  London,  is  illustrated  in  Fig.  178. 
Besides  giving  a  stronger  field,  large  field  magnets  have  the 
advantage  of  greatly  increased  magnetic  stability,  an  extreme- 
ly important  condition  in  securing  steadiness  of  the  lights. 
The  armature  is  drum-shaped,  and  is  wound  and  connected 
with  the  commutator  in  a  similar  manner  to  the  Siemens.  It, 
however,  differs  from  it  in  an  important  particular.  In  the 
Siemens  armature  the  wire  starts  from  a  commutator-plate, 
and  is  carried  a  number  of  times  around  the  cylindrical  core 
to  form  a  coil  of  many  strands.  It  is  then  brought  to  the  next 


276 


PRODUCTION  OF  ELECTRIC   CURRENTS. 


commutator-plate,  and  from  this  same  plate  another  wire  is 
taken  and  likewise  coiled  around  the  drum,  and  then  brought 
up  to  the  next  plate,  and  so  on.  In  the  Edison,  instead  of 
the  wire  being  coiled  over  the  drum  a  number  of  times,  each 
loop  is  brought  to  the  successive  commutator-plates,  so  that, 
starting  from  one  plate,  the  wire  passes  lengthwise  along 
one  side  of  the  drum 
across  the  farther  end, 
back  along  the  other 
side  of  the  drum,  up 
across  the  end,  and  is 


then  attached  to  the  ad- 
jacent commutator  -  plate. 
The  next  loop  starts  from 
this  plate  and  is  carried 
in  a  similar  manner  to  the 
next  plate.  The  size  of  this 
wire  increases  with  the  di- 
mensions of  the  machine 

until  it  is  replaced  by  copper  bars  connected  at  the  ends 
with  copper  disks.  This  construction  is  adopted  in  the  larger 
of  the  machines  designed  for  isolated  lighting  and  in  the  cen- 
tral-station dynamos.  The  inductive  portion  of  the  armature 
of  this  latter  machine  (Fig.  178)  is  composed  of  one  hundred 


FIG.  179.— Construction  of  the  armature  of  the 
Edison  steam  dynamo. 


RECENT  DYNAMO-ELECTRIC   MACHINES.  277 

and  eight  of  these  bars,  arranged  at  equal  distances  around  a 
cylindrical  core,  from  which  they  are  insulated.  These  bars 
are  connected  at  each  end  with  copper  disks  in  such  a  way 
as  to  form  a  metallic  circuit  along  one  bar,  across  the  end- 
disk,  along  the  diametrically  opposite  bar,  across  a  disk  at  the 
other  end,  then  along  the  bar  next  to  the  first  one,  and  so  on. 
As  stated,  connections  with  the  commutator-plates  are  made  at 
the  ends  of  each  bar  adjacent  to  the  commutator.  The  arma- 
ture core  is  made  up  of  a  great  number  of  sheet-iron  washers 
strung  upon  a  central  wooden  cylinder  and  insulated  from 
each  other  by  disks  of  tissue-paper.  The  details  of  construc- 
tion are  shown  in  Fig.  179,  in  which  C  C  are  the  copper  disks, 
and  B  B  the  bars  attached  to  them  by  means  of  bolts.  The 
sheet-iron  disks  forming  the  magnetic  core  are  shown  at  A, 
and  one  of  the  bolts  by  which  the  parts  of  the  armature  are 
securely  bound  together,  at  d.  The  commutator  is  shown  at 
D.  The  complete  armature  has  a  length  of  five  feet  and  a 
diameter  of  twenty-eight  inches,  and  weighs  over  four  tons. 
It  is  driven  at  a  speed  of  three  hundred  and  fifty  revo- 
lutions a  minute  in  the  cylindrical  cavity  formed  by  the 
curved  faces  of  the  field-magnet  poles.  It  has  a  resistance 
of  only  *00049  ohm.  The  field  magnets  consist  of  twelve 
cylindrical  cores,  wound  with  insulated  copper  wire,  which 
terminate  in  the  massive  pole-pieces  seen  in  the  front  of  the 
illustration,  and  are  connected  at  the  back  by  a  heavy  iron 
plate  or  yoke.  They  are  placed  in  a  shunt  circuit — that  is, 
a  circuit  arranged  so  that  the  current  divides  at  the  brushes, 
a  part  going  into  the  external  circuit  to  feed  the  lamps, 
and  the  rest  circulating  in  the  coils  of  the  field  magnet. 
The  magnet  coils  are  connected  together  so  as  to  form  two 
circuits  having  a  total  resistance  of  twenty-one  ohms.  The 
machine  is  driven  by  a  Porter- Allen  horizontal  engine  of  one 
hundred  and  thirty  horse-power.  It  is  connected  directly  with 
the  armature-shaft  without  the  intervention  of  belts.  The 
whole  apparatus,  including  the  bed-plate,  weighs  about  thirty 
tons.  Quite  recently  Mr.  Edison  has  modified  the  construction 
somewhat,  so  as  to  be  able  to  obtain  about  twenty  per  cent  more 
current  without  any  increase  of  the  cost  of  construction.  The 
present  machine  furnishes  a  current  of  eight  hundred  amperes 
under  an  electrical  pressure  of  one  hundred  and  fifteen  volts, 
while  the  new  one  gives  one  thousand  amperes  with  a  press- 
ure of  one  hundred  and  twenty  volts.] 


RECENT  DYNAMO-ELECTRIC  MACHINES.  279 

We  shall  terminate  this  review  of  the  machines,  adopted 
from  M.  Gramme's  system,  by  indicating  two  modifications 
invented  for  better  utilizing  the  portions  of  the  induced  wire 
which  are  included  in  the  interior  of  the  ring,  so  that  the  in- 
terior wires  are  equally  subjected  to  induction,  and  contribute 
to  the  production  of  currents  instead  of  opposing  thereto  a 
useless  resistance.  M.  Jurgensen  has  gone  further  ;  he  causes 
the  ring  to  move  between  two  field  magnets — one  interior,  the 
other  exterior.  The  exterior  magnet  is  composed  of  an  elec- 
tro-magnet with  two  arms,  whose  semicircular  poles  embrace 
the  ring  almost  completely,  in  the  ordinary  manner.  The 
wire  of  the  magnetizing  coils  is  accumulated  behind  the  poles 
in  more  numerous  layers,  to  re-enforce  their  power. 

The  interior  magnet,  which  recalls  that  of  the  alternate- 
current  machines  of  Gramme,  is  formed  by  two  straight 
electro-magnets,  whose  poles  are  spread  out  in  the  form  of  a 
cylinder,  concentric  with  the  ring.  This  inner  magnet  is  sta- 
tionary, and  supported  so  that  the  ring  turns  freely  between 
these  double  poles. 

IV.  TRANSFORMATIONS  or  THE  PRECEDING  MACHINES. 

One  of  the  first  means  invented  for  diminishing  as  much 
as  possible  the  quantity  of  inactive  wire,  was  to  transform  the 
cylindrical  ring  into  a  flattened  disk,  on  whose  faces  the  field 
magnets  acted  laterally.  It  was  thus  that  were  formed  a  new 
series  of  machines,  based  on  the  same  principles,  and  differ- 
ing only  in  the  form  of  armature  ;  such  are,  among  others,  the 
machines  of  Messrs.  Schuckert,  Ball,  Gulcher,  and  Brush. 
We  shall  examine  this  last,  which  is  interesting  from  the  re- 
sults which  it  gives,  and  from  the  particular  character  of  the 
system  of  lighting  of  which  it  forms  a  part. 

The  field  magnets  of  the  Brush  machine  (Fig.  181)  are 
composed  of  two  very  powerful  electro-magnets,  whose  arms 
are  terminated  by  polar  plates  in  the  form  of  sectors,  suffi- 
ciently extended  for  three  of  the  armature  coils  to  be  con- 
tained at  once  within  each  polar  space.  Here  it  is  the  similar 
poles  which  face  each  other.  It  follows  from  this,  on  account 
of  the  form  and  thickness  of  the  armature  disk,  that  there 
are  four  magnetic  fields,  alternated  two  by  two. 

The  armature  has  for  core  a  cast-iron  ring,  of  rectangular 
section,  in  which  are  formed  on  each  side  as  many  grooves  as 


RECENT  DYNAMO-ELECTRIC   MACHINES. 


281 


FIG.  182.— Cross- 
section  of  the 
Brush  ring. 


there  are  coils  to  be  received ;  the  projections  that  are  left, 
and  which  separate  the  coils,  form  a  series  of  polar  projections 
designed  to  react  laterally ;  the  division  is  made  in  even  num- 
bers, so  that  the  coils  are  diametrically  opposite. 
,. Four  concentric  grooves  are  cut  in  each  lat- 

eral face  of  this  ring,  and  a  circular  groove 
separates  it  almost  completely  into  two  disks, 
which  play  the  role  of  two  juxtaposed  mag- 
netic screens  (Fig.  182  and  183) ;  thus  the  for- 
mation of  local  currents  is  diminished,  and  a 
large  cooling  surface  is  obtained. 

The  armature  wire  is  wound  in  the  grooves, 
which  it  fills  completely,  so  that  the  lateral 
faces  of  the  ring  and  of  the  coils  are  in  the 
same  plane  (Fig.  184) ;  all  the  coils  are  wound 
in  the  same  direction.  The  induction  currents 
produced  by  the  passage  of  the  radial  wires 
through  the  two  opposite  magnetic  fields  are  of  contrary 
direction,  not  only  on  each  of  the  faces  of  the  ring,  but  also 
in  the  coils  situated  at  the  extremities  of  the  same  diameter, 
so  that  if  the  incom- 
ing wire  of  one  of 
them  has  a  +  sign, 
the  incoming  wire  of 
the  other  will  have 
the  —  sign ;  the  coils 
are  coupled,  two  by 
two,  by  connecting 
their  incoming  wires, 
and  the  outgoing 
wires,  left  free,  rep- 
resent poles  of  con- 
trary name  of  each 
of  the  circuits  thus 
formed,  and  are  led 
to  the  commutators. 
Instead  of  a  sin- 
gle Commutator,  Mr.  Fio.  183.— Construction  of  the  Brush  ring. 

Brush  uses  as  many 

commutator  rings  as  there  are  pairs  of  induced  coils ;  and 
each  of  these  commutators  is  divided  into  three  insulated 
segments  (Fig.  185) :  one  (C)  represents  only  one  eighth  of 


282 


PRODUCTION  OF  ELECTRIC  CURRENTS. 


the  circumference,  the  remainder  of  which  is  divided  between 
the  two  others  (A  B) ;  besides,  the  commutators  are  connected 
in  two  pairs,  on  each  of  which  two  elastic  brushes  rest  to 
collect  the  currents. 

For  a  ring  containing  eight  coils,  there  are  four  commuta- 
tors, whose  eight  large  segments  are  connected  with  the  out- 


Fio.  184.— Brush  armature,  with  its  coils  in  position. 

going  wires  of  four  pairs  of  coils ;  each  of  the  segments  of 
the  same  ring  receives  a  wire  of  opposite  sign.  The  small 
segments  receive  no  wire,  and  are  completely  insulated. 

We  have  seen  that  there  were  three  coils  induced  at  once 


RECENT  DYNAMO-ELECTRIC  MACHINES. 


283 


r --». 


FIG.  185. — Cross-section  of  Brush 
commutator. 


in  each  of  the  interpolar  spaces ;  there  remain,  then,  two 
in  the  neutral  spaces,  in  which  the  currents  produced  are 
insignificant,  and  do  not  compensate 
for  the  loss  due  to  the  resistance  of 
their  wires.  Mr.  Brush  has  pre- 
ferred to  cut  them  out  of  the  circuit 
at  the  moment  they  traverse  the  neu- 
tral spaces,  which  is  when  one  of  the 
small  completely  insulated  segments 
passes  before  the  brushes. 

In  the  three  pairs  of  active  coils, 
two  are  associated  in  quantity  by 
the  simultaneous  passage  under  the 
brushes  of  the  segments  representing 
them,  and  supply  the  working  current  of  the  outer  circuit. 
The  third  pair  form  a  special  circuit  devoted  to  the  exciting 
of  the  field  ;  this  disposition  has  the  advantage  of  rendering 
the  exciting  current  independent  of  variations  in  the  exterior 
circuit.  In  consequence  of  the  movements  of  the  ring,  these 
change  their  rdles  alternately ;  but  the  division  of  functions 
remains  the  same. 

[Though  so  widely  used,  the  Brush  dynamo  appears  to  be 
but  little  understood.  It  seems  desirable,  therefore,  to  sup- 
plement the  description  above  given  with  the  following  clear 
and  concise  explanation  of  its  mode  of  operation  by  Professor 
Sylvanus  P.  Thompson,  in  his  lectures  on  "  Dynamo-Electric 
Machinery,"  before  the  Society  of  Arts. 

"Its  armature — a  ring  in  form,  not  entirely  overwound 
with  coils,  but  having  projecting  teeth  between  the  coils  like 
the  Pacinotti  ring — is  unique.  Though  it  thus  resembles  Paci- 
notti's  ring,  it  differs  more  from  the  Pacinotti  armature  than 
that  armature  differs  from  those  of  Siemens,  Gramme,  Edison, 
Burgin,  etc. ;  for  in  all  those  the  successive  sections  are  united 
in  series  all  the  way  round,  and  constitute,  in  one  sense,  one 
continuous  bobbin.  But  in  the  Brush  armature  there  is  no 
such  continuity.  The  coils  are  connected  in  pairs,  each  to 
that  diametrically  opposite  it,  and  carefully  isolated  from 
those  adjacent  to  them.  For  each  pair  of  coils  there  is  a  sepa- 
rate commutator,  so  thaty  for  the  ordinary  ring  of  eight  coils, 
there  are  four  distinct  commutators  side  by  side  upon  the 
axis — one  for  each  pair  of  coils.  The  brushes  are  arranged 
so  as  to  touch  at  the  same  time  the  commutators  of  two  pairs 


284 


PRODUCTION  OF  ELECTRIC   CURRENTS. 


of  coils,  but  never  of  two  adjacent  pairs ;  the  adjacent  com- 
mutators being  always  connected  to  two  pairs  of  coils  that 
lie  at  right  angles  to  one  another  in  the  ring.  The  arrange- 
ment is  best  studied  graphically  from  the  diagram  given  in 
Fig.  186.  In  this  figure  the  eight  coils  are  numbered  as  four 


FIG.  186.— Diagram  of  Brush  dynamo. 

pairs,  and  each  pair  has  its  own  commutator,  to  which  pass 
the  outer  ends  of  the  wire  of  each  coil,  the  inner  ends  of 
the  two  coils  being  united  across  to  each  other  (not  shown  in 
the  diagram).  In  the  actual  machine,  each  pair  of  coils,  as 
it  passes  through  the  position  of  least  action  (i.  e.,  when  its 
plane  is  at  right  angles  to  the  direction  of  the  lines  of  force 


RECENT  DYNAMO-ELECTRIC  MACHINES.  285 

in  the  field,  and  when  the  number  of  lines  of  force  passing 
through  it  is  a  maximum,  and  the  rate  of  change  of  these 
lines  of  force  a  minimum)  is  cut  out  of  connection.  This  is 
accomplished  by  causing  the  two  halves  of  the  commutator 
to  be  separated  from  one  another  by  about  one  eighth  of  the 
circumference  at  each  side.  In  the  figure  it  will  be  seen  that 
the  coils  marked  1,  1,  are  'cut  out.'  Neither  of  the  two 
halves  of  the  commutator  touches  the  brushes.  In  this  posi- 
tion, however,  the  coils  3,  3,  at  right  angles  to  1,  1,  are  in  the 
position  of  best  action,  and  the  current  powerfully  induced 
in  them  flows  out  of  the  brush  marked  A  (which  is,  therefore, 
the  negative  brush),  into  that  marked  A'.  This  brush  is  con- 
nected across  to  the  brush  marked  B,  where  the  current  re- 
enters  the  armature.  Now,  the  coils  2,  2,  have  just  left  the 
position  of  best  action,  and  the  coils  4,  4,  are  beginning  to 
approach  that  position.  Through  both  these  pairs  of  coils, 
therefore,  there  will  be  a  partial  induction  going  on.  Accord- 
ingly, it  is  arranged  that  the  current,  on  passing  into  B,  splits, 
part  going  through  coils  2,  2,  and  part  through  4,  4,  and  re- 
uniting at  the  brush  B',  whence  the  current  flows  round  the 
coils  of  the  field  magnets  to  excite  them,  and  then  round  the 
external  circuit,  and  back  to  the  brush  A.  (In  some  machines 
it  is  arranged  that  the  current  shall  go  round  the  field  mag- 
nets after  leaving  brush  A',  and  before  entering  brush  B  ;  in 
which  case  the  action  of  the  machine  is  sometimes,  though 
not  correctly,  described  as  causing  its  coils,  as  they  rotate, 
to  feed  the  field  magnets  and  the  external  circuit  alternately). 
The  rotation  of  the  armature  will  then  bring  coil  2,  2,  into  the 
position  of  least  action,  when  they  will  be  cut  out,  and  the 
same  action  is  renewed  with  only  a  slight  change  in  the  order 
of  operation.  The  following  table  summarizes  the  successive 
order  of  connections  during  a  half -revolution  : 

First  position.     (Coils  1  cut  out.) 

A  —  3  —  A ;  B  <  *  >  B ;  Field  magnets  —  External  circuit  —  A. 
Second  position.  (Coils  2  cut  out.) 

A  <  *  >  A ;  B  —  4— B;  Field  magnets  —  External  circuit  —  A. 
Third  position.  (Coils  3  cut  out.) 

A  —  1  —  A;  B  <  4  >  B  ;  Field  magnets  —  External  circuit  —  A. 
Fourth  position.  (Coils  4  cut  out.)  A^, 

q  ""'"'"   ' 

A  <  l  >  A ;  B  —  2  —  B;  Field  magnets  —  External  circuits  —  A. 


286  PRODUCTION  OF  ELECTRIC   CURRENTS. 

"  From  this  it  will  be  seen  that  whichever  pair  of  coils  is 
in  the  position  of  best  action  is  delivering  its  current  direct 
into  the  circuit ;  while  the  two  pairs  of  coils  which  occupy  the 
secondary  positions  are  always  joined  in  parallel,  the  same 
pair  of  brushes  touching  the  respective  commutators  of  both."] 

There  are  three  types  of  these  machines  that  can  supply 
respectively  six,  sixteen,  and  forty  lamps.  In  the  sixteen- 
lamp  machine  the  cores  of  the  field  magnets  are  wound  each 
one  with  about  900  metres  of  wire  of  four  millimetres  diame- 
ter ;  each  of  the  armature  coils  contains  about  270  metres  of 
wire  of  about  two  millimetres  thickness.  The  speed  is  750 
revolutions  per  minute,  and  the  power  expended  about  sixteen 
horse-power. 

The  Brush  machines  are  made  to  supply  currents  of  very 
high  tension,  which  admit  of  placing  all  the  lamps  in  a  single 
series,  whose  length  of  circuit  may  attain  ten  to  twelve  kilo- 
metres. In  the  experiments  in  lighting  made  in  Paris  in  the 
Theatre  de  1'Opera,  the  lamps  of  this  system,  which  lighted 
the  grand  staircase,  were  supplied  by  a  machine  placed  in  the 
Palais  de  1'Exposition  in  the  Champs-Elysees.  There  was 
evidently  a  great  economy  in  the  arrangement ;  but  the  use  of 
such  currents  requires  very  careful  insulation,  and  involves 
serious  dangers,  which  must  also  be  taken  into  account. 

The  description  of  the  other  machines  of  this  category 
would  exceed  the  limits  of  this  work ;  they  present  hardly 
any  peculiarities  of  interest,  with  the  exception  of  M.  Gulcher's 
machine,  in  which  the  field-magnet  poles,  that  face  each  other, 
are  connected  by  an  intermediary  piece  of  iron,  so  as  to  sub- 
ject to  induction  those  portions  of  the  wire  which  come  upon 
the  outside  surface  of  the  disk. 


V.  MACHINES  IN  WHICH  THE  CORES  OF  THE  ARMATURE 
COILS  PLAY  A  PREPONDERATING  ROLE. 

We  now  have  only  to  examine  those  machines  in  which 
the  changes  of  magnetic  state  of  the  iron  cores  of  the  arma- 
ture coil  play  a  preponderating  role,  as  was  the  case  in  the 
machines  of  Clarke  and  Nollet,  with  which  we  commenced. 
The  machines  of  Messrs.  Niaudet,  Wallace  and  Farmer,  and 
Lontin,  come  in  this  category  ;  the  machines  of  Messrs.  Bur- 
gin  and  De  Meritens  occupy  an  intermediate  position  between 
the  two  systems. 


RECENT  DYNAMO-ELECTRIC  MACHINES. 


287 


We  here  speak  of  the  machine  invented  by  M.  Maudet  in 
1872,  although  it  was  never  extensively  introduced,  because  it 
was  the  first  of  this  category  which  furnished  continuous  cur- 
rents ;  for  armature  it  had  a  series  of  bobbins  wound  on  iron 
cores ;  these  were  arranged  circularly  on  a  wooden  disk,  and 
turned  between  the  poles  of  two  parallel  magnets.  The  cur- 
rents were  collected  by  aid  of  a  commutator  like  that  of  M. 
Gramme. 

The  machine  of  Messrs.  Wallace  and  Farmer  (Fig.  187),  of 
which  much  has  been  said  during  the  last  two  years,  and 
which,  nevertheless,  did  not  figure  at  the  Electrical  Exhibi- 
tion, is  a  machine  analogous  to  that  of  M.  Maudet.  There  are 


FIG.  187. — Wallace-Farmer  machine. 

two  disks  of  iron  in  juxtaposition,  and  two  rows  of  bobbins  ; 
the  cores  are  flattened,  and  pierced  with  a  hole  to  increase  the 
cooling  surface  and  diminish  the  production  of  Foucault  cur- 
rents. In  these  machines  the  commutation  plane  is  coinci- 
dent with  that  passing  through  the  poles. 

M.  Lontin  had  constructed,  in  1874,  a  machine  in  the  same 
category,  but  with  the  armature  bobbins  differently  arranged. 
In  place  of  having  their  axes  parallel  to  the  axis  of  rotation, 
they  radiate  from  this  axis,  which  made  their  inventor  call 
them  pinion-machines. 

In  the  first  apparatus  of  this  system  the  armature  bobbins 
were  flat,  and  were  arranged  parallel  to  the  axis  of  rotation. 

20 


288  PRODUCTION  OF  ELECTRIC  CURRENTS. 

As  now  constructed  (Fig.  188)  the  cores  have  a  conical  form, 
designed  to  prevent  the  throwing  off  of  their  coils  under  the 
effect  of  centrifugal  force,  and  on  account  of  their  step-like 

arrangement  on  the  axis,  their  polar 
extremities  are  successively  presented 
at  equal  but  more  frequent  intervals, 
to  the  action  of  the  field-magnet  poles. 
These  are  better  utilized  and  the  cur- 
rents are  more  regular. 

The  copper-wire  coils  which  envelop 
these  cores  are  wound  all  in  the  same 

Lontin  continuous-current 

machine.  coming  wire  connected  to  the  outgo- 

ing wire  of  the  next  helix,  but  from 

one  ring  to  another  and  in  the  order  in  which  they  follow 
each  other  before  the  poles,  so  that  the  whole  forms  a  con- 
tinuous circuit. 

Wires  are  taken  from  these  junctions  to  the  plates  of  a 
commutator  similar  to  that  of  M.  Gramme,  but  the  brushes 
are  prisms  of  an  anti-friction  alloy ;  these  prisms  slide  in 
brass  grooves,  well  insulated,  and  are  pressed  on  the  com- 
mutator by  weights  or  springs. 

The  field  is  an  ordinary  electro-magnet  with  two  arms,  ex- 
cited by  the  current  of  the  machine  ;  the  poles  are  sometimes 
supplied  with  movable  extensions,  which  can  be  prolonged  or 
withdrawn  at  will,  to  regulate  their  action  on  the  armature. 
It  is  a  mode  of  regulation  different  from  that  which  we  have 
hitherto  seen ;  for  hand  regulating  it  seems  more  simple  to 
change  the  length  of  the  magnetizing  coils ;  on  the  other  hand, 
the  powerful  attractions  which  are  exerted  between  these 
pieces  and  the  cores  of  the  field  magnets  would  render  it  diffi- 
cult to  make  them  self -regulating. 

In  1876  M.  Lontin  constructed  on  the  same  plan  a  machine 
for  alternating  and  divided  currents,  with  a  movable  field  mag- 
net turning  in  the  middle  of  a  crown  of  fixed  armature  bob- 
bins, whose  currents  were  directly  collected. 

In  these  machines  the  movable  field  magnet  is  composed 
of  a  magnetic  pinion  of  the  same  inventor,  and  consists,  like 
the  preceding,  of  an  electro-magnet  of  multiple  poles  with 
radiating  cores,  having  as  common  connector  the  cylinder  to 
which  these  cores  are  fastened.  With  this  system  it  is  neces- 
sary, to  obtain  the  maximum  useful  effect  of  the  exciting  cur- 


KECEOT  DYNAMO-ELECTKIC  MACHINES.  289 

rent  on  the  entire  mass  of  iron  of  the  field  magnets,  that  the 
cores  should  present  in  equal  numbers  alternately  poles  of  the 
opposite  kind;  which  amounts  to  the  establishment  of  an 
equal  number  of  two-branch  electro-magnets  with  a  common 
base,  so  as  to  mutually  re-enforce  each  other.  This  result  is 
obtained  in  changing  the  direction  followed  by  the  current 
that  circulates  in  the  helices,  either  by  the  direction  of  the 
winding  or  by  the  mode  of  connecting  the  extremities  of  the 
different  coils  with  each  other. 

The  armature  is  composed  of  a  fixed  ring,  supplied  on  its 
inner  surface  with  cores  evenly  spaced  in  the  form  of  radii, 
giving  it  the  appearance  of  an  interiorly-toothed  wheel. 

The  field-magnet  poles  being  alternately  of  different  kind, 
the  polarity  of  the  armature  coils  also  alternates,  and  the  cur- 
rents created  at  the  same  instant  in  their  coils  have  directions 
opposite  to  each  other.  It  is  necessary,  therefore,  in  order  to 
obtain  them  of  similar  direction  and  to  be  able  to  couple  them, 
to  connect  together  the  wires  of  the  helices,  having  regard  to 
the  direction  in  which  the  currents  go — that  is  to  say,  to  unite 
alternately  the  incoming  ends  of  the  one  and  the  outgoing 
ends  of  the  others.  The  successive  currents  are  not  the  less 
reversed,  on  account  of  the  effect  due  to  the  removing  and 
approaching  of  the  field  magnets.  The  exciting  current  of  the 
field  is  furnished  by  a  continuous-current  machine  of  the  same 
inventor. 

It  is  with  such  machines  that  the  first  trial  was  made  in  1877 
of  electric  lighting  at  the  station  of  the  Paris,  Lyons,  and  Med- 
iterranean Railway,  and  it  is  these  which  are  to-day  in  use  in 
the  experiments  in  lighting  the  Place  du  Carrousel  in  Paris. 

The  machine  invented  by  M.  Burgin,  and  adopted  by  M. 
Crompton  for  his  system  of  lighting,  resembles  rather  the  ring 
machines  in  its  form  of  armature ;  but  it  comes  in  the  cate- 
gory of  the  preceding  machines  in  its  method  of  induction. 
The  magnetic  core  is  of  hexagonal  form,  and  is  composed  of 
annealed  iron  wire  ;  the  copper  wire  is  wound  transversely  on 
each  of  the  sides  of  the  hexagon,  which  is  thus  fitted  with  six 
distinct  bobbins,  a  little  thicker  in  the  center ;  the  portions 
of  the  core  forming  the  summits  of  the  hexagon  are  exposed, 
and  pass  very  close  to  the  field-magnet  poles  :  it  follows  that 
there  are  in  the  core  very  energetic  changes  of  magnetic  state, 
which  play  the  principal  role  in  the  production  of  currents. 

As  each  of  the  rings  thus  constructed  would  be  too  feeble,  a 


290  PRODUCTION   OF  ELECTRIC  CURRENTS. 

certain  number  are  united  on  the  same  axis,  by  arranging 
them  so  that  they  assume  the  form  of  a  drum  with  the  rows 
of  bobbins  arranged  spirally  on  it  (Fig.  189).  It  is  a  similar 
disposition  to  that  of  the  radiating  bobbins  of  M.  Lontin,  to 
obtain  the  same  result.  The  method  of  connection  is  the 
same,  that  is,  the  connections  from  bobbin  to  bobbin  follow 
each  other  from  the  first  bobbin  of  the  first  ring  to  the  first 
bobbin  of  the  last  ring,  which  in  its  turn  is  connected  with 
the  second  bobbin  of  the  second  ring,  and  so  on.  It  is  the 
sixth  bobbin  of  the  last  ring  which  communicates  with  the 


FIG.  189. — Drum-armature  of  the-Burgin  machine. 

second  wire  of  the  first  bobbin  of  the  first  ring,  and  thus  com- 
pletes the  circuit ;  from  each  of  these  junctions  a  wire  is  car- 
ried to  the  commutator,  which  contains  as  many  plates  as 
there  are  bobbins  in  the  drum. 

The  field  magnet  is  composed  of  two  electro-magnets  with 
flattened  cores  and  consequent  poles  ;  the  cores  and  poles  are 
of  cast-iron,  and  in  one  piece.  The  machine  can  excite  itself ; 
but  in  large  electric  lighting  plants,  using  a  number  of  ma- 
chines, it  is  preferable  to  employ  separate  exciters. 

The  speed  of  the  ring  is  usually  1,500  to  1,600  revolutions 
per  minute ;  a  machine  of  forty-eight  bobbins  can  supply 
three  or  four  Crompton  lamps  arranged  in  series  ;  the  expen- 
diture of  power  varies  with  the  intensity  of  the  light. 


CHAPTER  IX. 

RECENT  MAGNETO-ELECTRIC  MACHINES. 

WE  have  already  explained  that  it  is  the  character  of  the 
inductors  which  has  divided  machines  into  the  two  classes  of 
dynamo-electric  and  magneto-electric  machines.  This  last 


KECENT  DYNAMO-ELECTRIC  MACHINES.  291 

system,  which,  as  we  have  seen,  was  employed  in  Nollefs 
machines  (Alliance),  has  long  been  abandoned,  because  of  the 
size  and  weight  of  the  apparatus ;  it  is  only  used  for  small 
laboratory  machines,  and  all  the  other  machines  that  we  have 
so  far  examined  are  dynamo-electric. 

Magneto-electric  machines,  nevertheless,  possess  the  ad- 
vantages of  increased  simplicity,  and  of  great  regularity  in  the 
production  of  currents,  resulting  from  the  stability  of  the 
magnetic  field.  There  is  no  need  of  fearing  the  reversal  of 
polarity  of  the  inductors,  which  may  cause  the  passage 
through  their  magnetizing  coils  of  reversed  currents,  which 
sometimes  happens  in  electro- chemical  operations,  and  in  the 
charging  of  secondary  batteries,  Plante's  or  others.  In  some 
applications  of  electric  light,  especially  in  light-houses,  this 
simplification  of  machines,  and  this  certainty  of  a  greater 
steadiness  of  light,  have  such  importance  that  magneto-elec- 
tric machines  have  really  been  given  -the  preference.  It  is, 
without  doubt,  for  the  same  reasons  that  M.  de  Meritens  has 
taken  up  again  the  study  of  this  system,  and  has  obtained 
remarkable  results.  He  not  only  has  improved  the  construc- 
tion of  the  permanent  magnets,  and  has  given  them  a  much 
greater  power,  but,  what  is  more  important,  he  has  invented 
a  new  arrangement  of  armature  which,  by  its  annular  form, 
utilizes  more  completely  the  power  of  the  field  magnets. 

M.  de  Meritens  constructs  his  machines  of  three  different 
types  :  a  large  alternating-current  machine  for  powerful  effects 
—it  is  the  type  actually  employed  in  light-houses  ;  a  smaller 
alternating-current  machine  for  factory-lighting  ;  and,  finally, 
a  machine,  also  magneto-electric,  producing  continuous  cur- 
rents. 

The  light-house  model  (Fig.  190)  is  composed  of  five  series 
of  field  magnets  and  five  armature  rings  ;  each  series  with  its 
ring  constitutes  a  complete  machine,  and  the  whole  can  be 
considered  as  formed  of  five  machines  in  juxtaposition.  Each 
of  the  series  of  field  magnets  contains  eight  compound  horse- 
shoe magnets  arranged  in  star- shape,  so  that  their  poles  form 
a  circular  crown,  in  whose  interior  the  armature  ring  rotates. 
It  is  the  well-known  form  of  the  old  Alliance  machines,  but 
here  the  action  of  the  magnets,  instead  of  being  lateral,  is 
exercised  endwise,  directly  on  the  armature,  with  full  power. 

Each  magnet  is  composed  of  eight  plates  of  Allevard  steel, 
of  ten  millimetres  thickness,  bolted  together  and  strung  upon 


292 


PRODUCTION  OF  ELECTRIC  CURRENTS. 


brass  cross-bars  fastened  to  the  side-frames ;  adjusting-screws 
admit  of  exact  regulation  of  the  position  of  the  cross-bars, 
and  facilitate  the  putting  together  of  the  machine.  Each 


FIG.  190. — Magneto-electric  machine  of  M.  de  Me*ritens.    Lighthouse  type. 

group  of  horseshoe  magnets  weighs  about  twenty-seven  kilo- 
grammes, and  can  sustain  one  hundred  and  fifty.  The  forty 
weigh  altogether  1,080  kilogrammes. 

The  annular  armature  is  composed  of  a  series  of  flattened 
electro-magnets  arranged  in  the  arc  of  a  circle,  of  the  form 
shown  in  Fig.  191.  These  are  united  end  to  end  by  their 
poles,  and  fastened  between  the  projections  on  a  brass  wheel. 
They  are  separated  one  from  the  other  by  small  copper  plates. 

To  facilitate  the  changes  of  the  magnetic  state  of  the  cores 
and  diminish  their  heating,  these  are  formed  of  plates  of  soft 


RECENT  DYNAMO-ELECTRIC  MACHINES. 


293 


FIG.  191.— Details  of  the  De  Meritens 
armature. 


sheet-iron,  a  millimetre  in  thickness,  cut  out  with  a  punch. 
The  armature  wire  is  wound  transversely  on  these  cores,  and 
particular  care  is  taken  to  obtain  a  perfect  insulation,  as  well 
between  the  wire  and  core,  as  between  the  individual  coils  or 
turns.  The  spacing  of  the  bob- 
bins and  magnets  is  laid  out  with 
the  greatest  care ;  the  distances 
between  the  consecutive  poles  of 
two  neighboring  magnets,  and  be- 
tween the  poles  of  a  correspond- 
ing magnet,  are  exactly  equal, 
and  each  distance  corresponds  to 
the  length  of  two  complete  bob- 
bins. 

Each  ring  contains  sixteen  bob- 
bins wound  with  wire  one  milli- 
metre and  nine  tenths  in  diame- 
ter. The  total  weight  of  the  wire 
of  the  eighty  bobbins  is  from 
fifty-five  to  sixty  kilogrammes. 

All  the  coils  are  connected  in  a  single  circuit ;  but  since, 
from  the  arrangement  of  the  field  magnets,  the  armature  bob- 
bins pass  successively  in  front  of  poles  of  diiferent  name,  and 
since  the  currents  produced  are  in  opposite  directions  in  con- 
secutive bobbins  at  the  same  instant,  they  are  coupled  two 
and  two  by  their  positive  and  negative  wires.  The  diagram 
given  in  Fig.  192  shows  how  this  coupling  is  done,  which  ad- 
mits of  their  being  united  in  a  single  circuit,  whose  extreme 
ends  are  separately  connected  with  friction-rings,  mounted  on 
the  shaft  of  the  machine  and  properly  insulated.  We  have 

seen  that  the  currents  are  alter- 
nating, because  each  passage  in 
front  of  the  poles  is  composed 
of  two  periods,  one  of  approach, 
the  other  of  recession. 

The  five  rings  are  coupled  so 
as  to  furnish  two  distinct  cur- 
rents, which  can  be  combined  at 

pleasure.  These  currents  are  collected  on  four  rings  ;  brush- 
es, carried  by  long  springs,  bear  against  these  rings  and  con- 
nect them  with  the  four  binding- screws  whence  the  current 
is  taken. 


Fio.  192.— Diagram  of  the  De  Meritens 
armature  coils. 


294 


PRODUCTION"  OF  ELECTRIC  CURRENTS. 


According  to  experiments  made  in  Paris  by  M.  Allard,  di- 
rector in  the  light-house  service,  this  machine  furnished,  with 
M.  Serrin's  regulator,  an  average  luminous  intensity  of  636 


FIG.  193. — Magneto-electric  machine  of  M.  de  Meritens.    Workshop  type. 

carcels,  with  a  speed  of  790  revolutions  per  minute,  and  an 
expenditure  of  eight  horse -power,  or  nearly  eighty-five  car- 
cels per  horse-power. 

The  machine  called  factory-machine  (Fig.  193)  is  con- 
structed on  the  same  principles.  The  eight  compound  field 
magnets  are  placed  horizontal,  and  arranged  around  a  hollow 
cylinder ;  the  alternate  poles  are  joined  together,  and  form  a 
circular  crown  within  whose  interior  the  armature  ring  turns. 
Each  magnet  is  composed  of  twelve  plates  of  steel,  each  one 
4*5  millimetres  in  thickness.  The  total  weight  of  the  field 
magnets  is  about  160  kilogrammes.  The  armature  ring  is 
identical  with  that  of  the  large  machine. 

This  factory-machine  is  supplied  with  an  arrangement 
which  has  been  called  the  permutator-plate  (plateau  permu- 
tateuf),  and  which  is  capable,  by  the  simple  changing  of  me- 


KECENT  DYNAMO-ELECTKIC  MACHINES.  295 

tallic  pins,  of  grouping  the  armature  bobbins  so  as  to  vary 
the  conditions  of  the  current.  The  sixteen  bobbins  can  be 
connected  in  tension,  and  in  this  case  the  machine  can  supply 
four  Jablochkoff  candles,  or  five  Berjot  regulators,  of  eighteen 
to  twenty  carcels  each;  the  speed  is  1,000  revolutions  per 
minute,  and  the  motive  power  expended  is  about  three  horse- 
power. 

Two  currents,  from  eight  bobbins  in  tension,  can  also  be 
associated  in  quantity,  and  two  regulators  of  forty  to  fifty 
carcels  each  can  thus  be  supplied.  Finally,  connecting  the 
bobbins  four  in  quantity  and  four  in  tension,  the  machine 
supplies  a  regulator  of  one  hundred  carcels. 

Reducing  the  number  of  magnetic  fields  to  four,  M.  de 
Meritens  has  constructed  a  magneto-electric  machine  for  con- 
tinuous currents  which  possesses  all  the  advantages  belong- 
ing to  this  class  of  generators  (Fig.  194).  The  permanent 
magnets  form  four  groups,  composed  each  one  of  sixty-four 


Fia.  194. — M.  de  Meritens's  continuous-current  magneto-electric  machine. 

steel  plates  one  millimetre  in  thickness,  arranged  around  a 
cylindrical  brass  frame.  Their  extremities,  projecting  from 
this  frame,  form  four  cylindrical  surfaces  within  which  the 
ring  turns. 


296  PRODUCTION  OF  ELECTRIC   CURRENTS. 

The  ring  also  contains  sixteen  armature  bobbins,  but  the 
core-plates  are  cut  so  as  to  form  four  projections,  between 
which  the  wire,  as  wound,  forms  four  distinct  helices  (Fig. 
195).     These  bobbins  are  mounted  in  the  same  fashion  around 
a  brass  wheel ;   they  are  connected  in 
series,  like  those  of  a  Gramme  ring,  and 
wires  are  arranged  at  each  junction  so 
as  to  connect  them  with  the  sixty-four 
commutator-plates. 

The  use  of  four  magnetic  fields  in- 
™lves  two  commutation  planes,  placed 
machine  of  M.  de  Meritens.      like    those  we    have   already  seen    in 
the  octagonal  machine  of  M.  Gramme. 

There  are  then  four  brushes,  two  for  each  of  the  currents  col- 
lected at  the  same  instant — currents  which  can  be  utilized 
separately  or  combined  at  will. 

The  collector,  or  commutator,  is  mounted  within  the  brass 
cylindrical  frame,  which  prevents  all  displacement  of  the 
wires,  short  of  dismountings.  A  movable  brass  ring  serves 
as  support  for  the  axes  of  the  brush- carriers,  and  facilitates 
the  exact  regulation  of  the  points  of  contact  of  the  brushes 
on  the  commutator.  This  arrangement  also  makes  it  possible 
to  reverse  the  brushes  when  the  machine  is  to  be  used  as  an 
electro-motor. 

This  machine  is  preferable  to  the  dynamo-electric  machines 
for  charging  secondary  batteries.  Under  ordinary  circum- 
stances, when  the  battery  is  receiving  its  charge,  there  comes 
a  time  when  the  accumulated  power  of  the  battery  is  sufficient 
to  overcome  that  of  the  machine  furnishing  the  current. 

With  a  dynamo-electric  machine,  unless  a  special  safety 
apparatus  is  used,  the  direction  of  the  current  may  become 
reversed,  and  the  battery  discharge  itself  through  the  ma- 
chine. But  the  current,  thus  reversed,  changes  the  polarity 
of  the  field  magnets,  and  the  machine,  continuing  to  revolve, 
undoes  all  the  work  previously  accomplished  in  the  battery. 
With  permanent  magnets  in  the  field,  this  trouble  can  not 
occur. 

Besides  the  machines  which  we  have  passed  in  review, 
there  are  a  very  great  number  which  work  just  as  well,  but 
whose  description  would  take  up  too  much  space.  The  ex- 
planations which  we  have  given  will  make  their  working  easily 
understood,  the  differences  only  being  in  the  form  and  rela- 


RECENT  DYNAMO-ELECTRIC  MACHINES. 


297 


tive  positions  of  their  constituent  elements.  It  will  be  un- 
derstood that  we  can  not  assign  them  their  relative  values  ;  in 
general,  each  machine  is  part  of  a  system  for  which  it  is 
specially  devised,  and  the  results  of  experiments  represent 
rather  the  value  of  the  whole  than  that  of  the  particular 
machine. 

We  shall  summarize  briefly  only  the  chief  conditions  that 
have  to  be  observed.  The  machines  should  heat  as  little  as 
possible,  because  the  heat  thus  disengaged  is  a  loss  of  work,  and 
may  become  a  cause  of  destruction  of  the  insulation.  This 
production  of  heat  can  not  be  completely  avoided,  but  it  can 
be  reduced  by  diminishing  useless  resistances,  such  as  those 
of  wires  that  do  not  participate  in  the  production  of  currents. 
The  movable  metallic  cores  should  be  constructed  so  as  to 
diminish  the  production  of  local  or  Foucault  currents,  and  so 
as  to  prevent  the  circulation  of  those  which  can  not  be  entirely 
suppressed. 

The  armature  wire  should  be  divided  into  as  great  a  num- 
ber of  coils  as  possible,  so  that  the  partial  currents  shall  be 
weaker,  which  reduces  the  power  of  the  sparks  on  the  com- 
mutators ;  it  is  true  that  the  number  of  these  currents  must 
then  be  increased,  and  consequently  the  speed  of  the  moving 
parts ;  but  these  being  lighter  and  easier  to  balance,  can  re- 
volve without  inconvenience  at  enormous  speed,  before  the 
contemplation  of  which  electricians 
would  have  recoiled  some  years  ago. 

Finally,  the  field  magnets  should 
be  so  placed  as  to  utilize  well  their 
magnetic  power.  The  mechanical 
construction  should  be  such  as  to 
insure  the  stability  and  durability 
of  the  moving  parts,  which  ought  to 
revolve  very  close  to  each  other,  and 
under  the  influence  of  high  attrac- 
tion. 

The  rubbing  surfaces  should  have 

dimensions  larger  than  those  used  for  the  same  speed  in 
ordinary  machines ;  their  lubrication  must  be  insured  with 
absolute  certainty.  We  may  recall  on  this  subject  a  new 
arrangement  due  to  M.  Gravier.  The  bearings  are  full  of 
holes,  which  are  filled  with  plugs  of  graphite  ;  no  other  lubri- 
cation is  required — it  must,  on  the  contrary,  be  absolutely 


b  oo  .. 

S8°' 

8881 
888 


Fm.   196.  —  Gravier' s    plumbago 
commutator-brushes. 


298  PRODUCTION  OF  ELECTRIC  CURRENTS. 

forbidden — nor  is  any  repairing  needed,  and  no  heating  need 
be  feared. 

M.  Gravier  uses  the  same  plan  for  his  commutator-brushes, 
which  he  constructs  as  shown  in  Fig.  196,  and  which  press 
against  a  disk  turning  vertically.  This  disk  carries  pieces  of 
copper  arranged  like  the  plates  of  ordinary  commutators. 


CHAPTER  X. 

EFFICIENCY  OF  THE  DYNAMO. 

[PERHAPS  no  term  is  commonly  used  more  loosely,  in  its 
application  to  the  dynamo  and  the  electric  system  of  which 
it  forms  a  part,  than  efficiency.  As  is  well  known,  this  term 
indicates  the  completeness  with  which  any  machine  or  appa- 
ratus utilizes  the  work  expended  upon  it,  but  it  does  not 
always  seem  to  be  remembered  that  it  may  have  very  differ- 
ent values,  depending  upon  the  quantities  between  which  it 
expresses  the  relation. 

A  brief  consideration  of  the  efficiency  of  machines  in 
general  may  perhaps  be  of  service  in  helping  us  to  a  clear 
conception  of  its  proper  use  in  its  application  to  electric  ap- 
paratus. 

Machines  may  be  broadly  divided  into  two  classes — trans- 
mitters and  transformers.  Wind-mills,  water-wheels,  and 
pumps  belong  to  the  first  class  ;  heat-engines,  electric  batter- 
ies, dynamos,  and  electro-motors  to  the  second.  The  former 
do  not  convert  energy  in  one  form  into  some  other  form,  but 
simply  serve  to  redirect,  in  such  a  way  as  to  be  serviceable, 
the  original  mechanical  energy.  For  instance,  in  a  water- 
wheel  the  energy  of  the  moving  mass  of  water  is  in  part 
transferred  to  the  wheel,  the  motion  of  which  we  can  utilize  ; 
or,  in  the  case  of  a  pump,  the  mechanical  energy  spent  in 
operating  it  is  utilized  in  giving  motion  or  position  to  water. 
In  either  case  there  is  no  transformation  of  energy,  but  sim- 
ply a  transference  of  motion  from  one  mass  to  another. 
We  start  with  energy  in  the  mechanical  form  and  end 
with  it  in  the  same  form,  without  any  intermediate  trans- 
formation. 


EFFICIENCY  OF  THE  DYNAMO.  299 

In  the  second  class  of  machines  there  is  always,  on  the 
other  hand,  a  transformation  of  energy.  In  the  steam  and 
other  heat  engines  the  original  work  is  in  the  form  of  heat, 
and  in  the  final  result,  in  that  of  mechanical  energy.  In  the 
dynamo  we  have  the  conversion  of  mechanical  energy  into 
that  of  electric  currents,  and  in  the  electro-motor  the  reverse 
operation;  while  in  the  electric  battery  we  have  the  direct 
transformation  of  the  work  of  chemical  combination  into  elec- 
trical energy. 

In  the  water-wheel  and  similar  machines,  we  may  distin- 
guish two  efficiencies  :  one  the  ratio  of  the  gross  return  of  the 
wheel  to  the  total  work  of  the  falling  water,  the  other  the 
ratio  of  the  utilizable  work  to  this  latter.  A  portion  of  the 
work  done  by  the  wheel  is  expended  in  overcoming  friction, 
etc.,  and  only  the  work  above  this  is  disposable.  The  ratio 
of  this,  which  may  be  measured  by  a  dynamometer,  to  the 
total  work  of  the  falling  water,  expresses  the  net  or  commer- 
cial efficiency  as  distinguished  from  what  may  be  termed  the 
gross  efficiency.  The  former  efficiency  is  the  one  which  alone 
concerns  the  user  of  the  machine,  and  which  is  always  meant 
in  tests  of  such  wheels.  In  the  water-wheel,  or  a  well-designed 
steam-engine,  the  difference  between  these  two  efficiencies  is 
not  great,  but  it  may  in  some  instances — in  the  hot-air  engine, 
for  example — be  very  considerable. 

A  heat-engine  of  any  form — steam,  gas,  or  hot  air — oper- 
ates by  taking  into  the  cylinder  a  working  -  fluid  at  one 
temperature  and  discharging  it  at  another,  the  proportion 
of  the  heat  utilized  depending  upon  the  difference  of  these 
'temperatures.  We  know  from  therm o-dynamics  just  how 
large  a  portion  this  can  be  in  a  perfect  engine.  This  theo- 

T  — T' 
retical  maximum  is  expressed  by  the  formula  — — — ,  in  which 

T  is  the  temperature  of  the  working-fluid  on  admission  to  the 
cylinder,  and  T'  the  temperature  at  discharge,  both  tempera- 
tares  being  reckoned  from  the  absolute  zero  ( — 461°  F.  and 
-  273°  C.).  Between  the  limits  of  temperature  practicable 
in  the  steam-engine,  this  maximum  efficiency  does  not  exceed 
twenty  per  cent.  The  work  done  by  the  expanding  fluid  in 
moving  the  piston  is  measured  by  the  product  of  the  mean 
pressure  upon  it,  and  the  distance  through  which  it  is  moved. 
The  ratio  of  this  work  to  the  work  in  the  steam  which  was 
necessary  to  yield  it,  gives  the  efficiency  of"  the  engine  as  a 


300  PRODUCTION"  OF  ELECTRIC  CURRENTS. 

transformer  of  lieat  into  mechanical  energy.  In  the  best  of 
modern  engines  this  efficiency  is  from  sixty  to  seventy  per 
cent  of  the  theoretical  maximum,  or  twelve  to  fourteen  per 
cent  of  the  work  in  the  steam. 

The  efficiency  of  a  steam-engine  is  not,  however,  usually 
reckoned  in  this  manner.  It  is  commonly  expressed  by  the 
ratio  of  the  work  performed  by  it  to  that  of  the  fuel  burned 
in  the  furnace.  This,  of  course,  does  not  give  simply  the 
efficiency  of  the  engine,  but  the  combined  efficiency  of  the 
engine  and  boiler.  But  as  in  practice  these  two  constitute 
one  machine,  it  is  the  efficiency  of  this  with  which  the  con- 
sumer is  concerned.  In  this  case  the  efficiency  of  transforma- 
tion is  expressed  by  the  relation  of  the  work  done  upon  the 
piston  to  that  to  which  the  fuel  burned  to  produce  it  is 
equivalent.  As  stated  above,  the  former  work  is  obtained  by 
multiplying  the  mean  pressure  upon  the  piston  by  the  dis- 
tance through  which  it  is  moved.  In  ordinary  units,  the  power 
is  therefore  expressed  by  the  total  mean  pressure  on  the 
piston  in  pounds,  multiplied  by  the  piston  travel  per  minute 
in  feet.  This  divided  by  33,000  gives  the  horse-power  exerted 
by  the  engine,  generally  known  as  the  indicated  horse-power, 
on  account  of  the  manner  in  which  the  mean  steam-pressure 
is  obtained.  Taking  the  fuel-consumption  as  two  pounds  of 
coal  an  hour  per  indicated  horse-power,  we  have  the  efficiency 
of  transformation,  regarding  a  pound  of  coal  as  equivalent 

to  10,000,000  foot-pounds,  equal  to  ('      '        )  one  tenth 

V  ^0, 000,  000  / 

nearly.  The  actual  or  available  horse-power  of  the  engine 
will  evidently  be  the  difference  between  the  indicated  horse- 
power and  that  required  to  move  the  engine  simply,  and  the 
net  or  commercial  efficiency  the  ratio  of  this  actual  horse- 
power to  that  of  the  fuel  expended.  In  a  good  modern  en- 
gine, the  actual  is  eighty-eight  per  cent  of  the  indicated  horse- 
power. 

We  are  now  in  a  position  to  better  understand  the  various 
efficiencies  of  the  dynamo,  and  of  an  electric  system.  There  is 
first  the  efficiency  of  transformation  of  mechanical  into  elec- 
tric energy,  usually  termed  the  "  generative  efficiency."  The 
relation  here  is  that  between  the  power  required  to  turn  the 
armature  in  the  magnetic  field  at  a  given  rate,  and  the  electri- 
cal power.  From  this  first  power  that  required  to  overcome 
the  friction  of  the  moving  armature  must  be  deducted,  as 


EFFICIENCY  OF  THE  DYNAMO.  301 

this  friction  does  not  contribute  to  the  electrical  result.  This 
net  power  is  obtained  by  measuring,  by  means  of  a  dyna- 
mometer, the  power  required  to  revolve  the  armature  when 
electrical  work  is  being  done,  and  subtracting  from  this  the 
power  required  to  drive  it  when  no  electrical  work  is  per- 
formed. The  electrical  power  in  watts  is  the  product  of  the 
current  flowing  through  the  circuit,  by  the  electro-motive 
force.  In  the  " series  dynamo"  there  is  but  one  circuit,  and 
the  current  in  it  is  of  course  the  total  current  flowing  ;  but  in 
the  " shunt  dynamo"  the  total  current  is  the  sum  of  those  in 
the  main  and  field  circuits.  The  difference  of  potential  to  be 
measured  is  that  between  the  binding-posts  of  the  machine, 
when  the  shunt  is  taken  directly  from  the  brushes,  as  is 
usually  the  case.  Denoting  the  net  power  by  P,  and  the 
electrical  power  by  p,  we  have- 
Generative  efficiency  =  —  (1) 

As  no  machine  can  be  made  frictionless,  the  practical  gen- 
erative efficiency  will  be  expressed  by  the  relation  between 
the  electrical  power  and  the  total  power  applied  to  the  pulley 
of  the  dynamo,  which  we  may  distinguish  as  the  gross  or 
dynamometrical  power.  Denoting  this  by  P ',  we  have — 

Practical  generative  efficiency  =  —  (2) 

The  amount  of  work  done  by  an  electric  current  in  any 
part  of  its  circuit  depends  upon  the  resistance  encountered. 
As  the  machine  has  resistance,  this  work  can  not  be  performed 
entirely  in  that  part  of  the  circuit  external  to  it,  but  its  amount 
will  depend  upon  the  relative  resistance  of  this  circuit  and 
the  machine.  The  ratio  of  this  portion  to  the  total  electrical 
work  expresses  the  electrical  efficiency.  For  a  long  time  it 
was  supposed  that  the  law  of  Jacobi — stating  that  the  maxi- 
mum electrical  work  was  obtained  from  a  generator  when 
its  resistance  was  equal  to  that  of  the  external  circuit — was 
a  law  of  efficiency,  but  we  now  know  that  this  is  not  the 
case. 

Instead  of  being  limited  to  a  maximum  of  only  one  half 
of  the  electrical  work  in  the  external  circuit,  we  can  get  a 
much  larger  portion  of  it  if  the  relative  resistances  of  this 
circuit  and  the  generator  are  rightly  proportioned.  Sir  Will- 
iam Thomson  has  shown  *  what  these  relations  should  be  in 

*  "British  Association  Report,"  1881. 


302  PRODUCTION  OF  ELECTRIC  CURRENTS. 

each  of  the  two  types  of  machine— the  series  and  shunt 
dynamo.     In  the  series  machine,  denoting  the  resistance  of 
the  external  circuit  by  R,  that  of  the  field-magnet  coils  by  R', 
and  of  the  armature  by  R",  we  shall  have — 
internal  work  R'  +  R" 


total  work         R  +  R'  +  B/ 
external  work  R 


and 


total  work         R  +  R/-f  R/'. 

He  also  showed  that  for  the  most  economical  working  R" 
should  be  slightly  greater  than  R'. 

In  the  shunt  dynamo,  these  resistances  should  be  related 
to  each  other  so  that  R  =  4/fi/  x  R",  and  the  maximum  work 
is  available  in  the  external  circuit  when 
external  work  1 


total  work 


/Wf 


Denoting  the  external  electrical  power  by  p',  we  have  — 

p' 

Electrical  efficiency  =  —  (3) 

P 

The  relation  of  the  external  electrical  to  the  dynamomet- 
rical  power  is  the  one  upon  which  the  commercial  excellence 
of  a  dynamo  depends.  This  may  be  termed  the  commercial 
efficiency.  We  have,  then,  as  a  last  efficiency  for  the  dynamo  — 

Commercial  efficiency  =  —  (4) 

There  are,  then,  four  efficiencies  properly  attributable  to 
the  dynamo,  the  first  two  of  which  determine  the  comparative 
merits  of  different  machines  as  generators,  bat  only  the  last 
of  which  enables  us  to  judge  of  their  value  as  commercial  ap- 
paratus. But  even  with  this  efficiency  given,  additional  data 
are  necessary  to  determine  the  economy  of  different  sets  of 
apparatus.  Of  the  electrical  energy  in  the  external  circuit 
only  a  part  is  available,  as  some  portion  is  expended  in  over- 
coming the  resistance  of  the  conductors.  With  currents  of 
small  quantity  and  high  tension  this  portion  may  be  small, 
but  it  may  be  very  considerable  in  the  case  of  currents  of 
large  volume  and  low  tension.  Depending  upon  the  character 
of  the  currents  used  in  any  system,  there  will  therefore  be  a 
further  efficiency  expressing  the  relation  between  the  -gross 
power  applied  to  the  pulley  of  the  dynamo,  and  that  in  the 
external  circuit  which  may  be  used.  This  may  be  properly 


EFFICIENCY  OF  THE  DYNAMO.  303 

termed  the  efficiency  of  the  system.     Denoting  this  utilizable 
power  by  p",  we  have — 

P" 

Efficiency  of  system  =  ^  (5) 

While  this  last  efficiency  enables  us  to  judge  of  the  elec- 
trical excellence  of  a  system,  it  does  not  necessarily  inform 
us  of  the  comparative  merits  of  different  systems  in  furnish- 
ing light.  In  this  estimate  another  factor — the  economy  of 
the  lamp — comes  in  as  an  element  in  determining  the  relation 
between  the  light  yielded  and  power  applied  to  the  pulley  of 
the  dynamo.  In  the  case  of  a  plant  consisting  of  a  dynamo  and 
arc-lamps,  this  relation  maybe  termed  the  "lighting  econo- 
my," but  it  must  not  be  confounded  with  an  efficiency,  for  it 
must  be  remembered  that  we  can  not  speak  of  the  efficiency 
of  an  arc  or  incandescent  lamp  in  the  same  way  as  that  of  a 
dynamo-machine  or  an  electrical  system.  In  the  latter  we  have 
an  ascertained  limit  beyond  which  we  can  not  go,  and  our  effi- 
ciency simply  expresses  the  nearness  of  approach  to  this  limit. 
We  know  that  for  every  foot-pound  of  work  done  upon  the 
pulley  of  a  dynamo  we  can  not  get  more  than  a  foot-pound  of 
work  in  the  electrical  circuit ;  we  know,  in  fact,  that  we  can 
get  but  a  portion  of  it.  In  the  case  of  a  lamp,  on  the  other 
hand,  we  have  not  a  well-defined  limit  to  the  light  obtainable 
with  a  given  amount  of  power.  There  is  certainly  a  limit,  but 
the  data  to  enable  us  to  determine  it  are  at  present  wanting. 
In  discussing  the  conditions  of  efficiency  in  incandescent  lamps 
it  was  pointed  out  that  the  maximum  economy  was  attained 
when  the  rate  of  the  generation  of  heat  per  unit  surface  was  as 
great  as  possible.  The  same  condition  applies  to  the  arc-light, 
though  here  it  is  not  so  evident  just  what  relations  the  various 
factors  which  have  to  be  considered — strength  of  current,  elec- 
tro-motive force,  and  size  of  electrodes — should  bear  toward 
each  other  to  realize  it.  Given  a  definite-current  strength,  it 
seems  very  probable  that  there  is  a  particular  electro-motive 
force  and  size  of  carbons  which  will  make  the  light  a  maxi- 
mum. If  the  carbons  be  too  large,  there  will  be  undue  cooling 
by  conduction  ;  and  if  the  arc  be  too  short,  the  incandescent 
surface  will  be  increased  and  its  temperature  lowered,  both  on 
account  of  increased  cooling  by  the  air,  and  a  less  rate  of  heat 
generation  per  unit  of  area.  This  latter  consideration  would 
lead  us  to  expect  that  a  long  arc  would  be  the  more  economi- 
cal, and  experience  appears  to  justify  this  conclusion,  though 
21 


304  PRODUCTION  OF  ELEOTEIC   CURRENTS. 

it  can  not  be  said  that  the  tests  made  of  lamps  of  short  and 
long  arc  have  as  yet  settled  the  matter.  So  far  as  I  am  aware, 
no  experiments  have  been  made  to  determine  this  question 
solely,  though  it  would  naturally  seem  to  be  one  to  which 
attention  would  have  been  early  given  by  those  engaged  in 
the  commercial  development  of  the  arc-lamp. 

The  practical  limit  to  the  amount  of  light  which  a  given 
heat-expenditure  can  be  made  to  yield  in  the  arc-lamp  is  de- 
pendent upon  the  consumption  of  the  carbons.  As  the  carbon 
particles  are  dissipated — both  by  combustion  and  by  being 
thrown  off  from  the  electrodes — it  is  clear  that  it  is  no  longer 
possible  to  impart  heat  to  them,  and  therefore  raise  their  tem- 
perature. Were  it  possible  to  obtain  electrodes  which  would 
remain  unchanged,  their  temperature  could  be  carried  up 
indefinitely,  and  the  amount  of  light  would  then  reach  the 
theoretic  limit.  This  limit,  it  has  been  previously  suggested, 
is  to  be  found  at  the  point  where  an  additional  increment  of 
temperature  ceases  to  produce  a  proportional  increase  of  light. 
Though  we  find  that  as  the  temperature  is  raised  an  increas- 
ing portion  of  the  total  radiation  is  luminous,  we  are  not 
warranted  in  assuming  that  it  would  all  become  so  with  an 
indefinite  augmentation  of  temperature.  For  it  must  be  re- 
membered that  while  there  goes  on  at  one  end  of  the  spectrum 
a  transformation  of  heat- vibrations  into  luminous  ones  of 
shorter  period,  there  goes  on  at  the  other  end  the  transfor- 
mation of  the  most  rapid  light- vibrations  into  others  still  more 
rapid,  which  are  as  incapable  of  exciting  vision  as  are  the 
longer-period  ones  at  the  red  end.  It  would  seem,  therefore, 
that  there  is  a  maximum  point  beyond  which  in  either  direc- 
tion there  would  be  a  less  amount  of  light  yielded  per  unit  of 
heat.] 


CHAPTER  XI. 

MEASUREMENTS   OF  DYNAMOS  AND  ARC-LAMPS. 

[THE  foregoing  considerations  enable  us  to  understand 
clearly  what  factors  must  be  determined  in  measuring  dyna- 
mos and  arc-lamps  in  order  to  judge  of  the  comparative  merits 
of  different  sets  of  apparatus.  The  final  relation  to  be  ar- 


MEASUREMENTS  OF  DYNAMOS  AND  ARC-LAMPS.         305 

rived  at  is  of  course  that  between  the  gross  power  applied  to 
the  pulley  of  the  dynamo  and  the  light  yielded,  and  for  com- 
mercial purposes  this  is  ordinarily  enough.  But  to  form  an 
intelligent  opinion  of  the  inherent  excellence  of  a  system — to 
know  wherein  it  is  good  and  wherein  bad — it  is  necessary  to 
have  all  of  the  data  indicated  above. 

It  would  seem,  at  first  sight,  a  comparatively  easy  matter 
to  measure  accurately  a  dynamo  and  set  of  arc-lamps,  but 
the  numerous  measurements  made  by  different  observers  pre- 
sent very  few  points  of  agreement,  while  in  the  same  set  of 
experiments  there  are  often  great  discrepancies.  The  measure- 
ments most  difficult  to  make  with  accuracy  are  those  of  the 
horse-power  applied  to  the  machine,  and  the  determination 
of  the  luminous  intensity.  This  latter,  in  the  case  of  the  arc- 
lamp,  is  a  very  uncertain  matter,  as  the  arc  is  constantly 
shifting,  and  the  intensity  of  the  light  varies  with  every 
change  of  angle  under  which  it  is  observed.  In  order  to  get 
a  measurement  which  would  give  the  average  illumination 
afforded  by  the  lamp,  the  plan  has  been  adopted  of  measur- 
ing the  light  in  all  directions  and  taking  their  mean.  This 
method  was  first  employed  by  the  Paris  committee  of  1881, 
and  has  since  been  generally  used  in  similar  tests.  It  has 
been  termed  the  moyenne  spheriqiie  intensity,  as  it  corre- 
sponds to  the  strength  of  the  light  at  every  point  of  a  sphere 
of  which  the  arc  is  the  center.  It  has  the  disadvantage  of 
giving  a  lower  candle-power  than  the  lamp  actually  yields,  as 
in  all  arc-lights  but  a  comparatively  small  portion  of  the  rays 
are  directed  upward,  but  this  does  not  detract  from  its  merits 
in  comparative  measurements. 

Of  the  many  tests  made  of  arc-lamps  and  dynamos  in  the 
past  few  years,  it  will  be  sufficient  to  give  here  those  of  the 
committee  of  the  Paris  Exposition  of  1881,  as  these  are  very 
complete  and  include  the  better  known  and  more  successful 
of  this  class  of  apparatus.  The  table  is  sufficiently  clear  to 
render  explanation  unnecessary,  though  one  or  two  points 
require  mention.  The  horse-power  is  given  in  French  meas- 
ure, which,  as  has  been  before  stated,  is  equal  to  75  kilogram- 
metres  per  second,  or  735*75  watts.  It  wfll  be  seen  that  the 
first  of  the  percentages  corresponds  to  efficiency  (2),  and  the 
second  to  efficiency  (5),  as  given  in  the  previous  chapter. 
The  third  gives  the  relation  between  the  total  electrical  work 
and  that  which  is  available  in  the  arcs.  The  number  of  car- 


306 


PRODUCTION  OF  ELECTRIC  CURRENTS. 


Table  of  Experiments  made  with  Oon- 


BY    THE    COMMITTEE    APPOINTED   AT 


Formulae. 


Gramme.  - 

1  lamp,  il  lamp. 


MECHANICAL    MEASUREMENTS. 

Speed  of  generator,  revolutions  per  minute 475 

Effective  power  applied,  horse-power T  16'13 

ELECTRICAL   MEASUREMENTS. 

Resistance  of  generator,  in  ohms r  0'33 

Resistance  of  mains  (circuit  without  lamps),  in  ohms r'  O'lO 

Resistance  of  mains  and  generator R  0*43 

Strength  of  current,  in  amperes I  109-2 

Fall  of  potential  at  each  lamp,  in  volts E  53'0 

ELECTRICAL   CALCULATIONS. 

RP 

Energy  in  generator  and  mains,  horse-power 697 

El 

Energy  in  one  lamp,  horse-power - —  7'87 

Energy  in  all  the  lamps,  horse-power t  7'87 

Total  electrical  energy,  horse-power ,,....' T'  14'84 

Mean  electro-motive  force nE  +  RI        102 

MEASUREMENTS   OF   LIGHT. 

Diameter  of  carbons,  in  millimetres 20 

Horizontal  intensity,  each  lamp,  carcels 952 

Maximum  intensity,  each  lamp,  carcels 1,960 

Mean  spherical  intensity,  each  lamp,  carcels 1  966 

Total  mean  spherical  intensity,  all  lamps,  carcels L=  nl  966 

RESULTS. 

T' 

Percentage  of  applied  power  converted  into  electrical  energy  . .  —  0'92 

Percentage  of  applied  power  appearing  in  the  arcs —  0'4 

Percentage  of  total  electrical  energy  appearing  in  the  arcs. . . .  0'53 

Carcels  per  horse-power  applied  to  generator — 

Carcels  per  horse-power  of  electrical  energy —  65'1 

Carcels  per  horse-power  of  energy  appearing  in  the  arcs 128'8 

1 

Carcels  per  ampere —  8'85 


MEASUREMENTS  OF  DYNAMOS  AND  ARC-LAMPS. 


SOT 


tinuous-Current  Generators  and  Lamps. 


THE   PARIS   EXPOSITION   OF    1881. 


3 
Maxim. 
1  lamp. 

4 
Siemens. 
1  lamp. 

5 

Siemens. 
2  lamps. 

6 
B  virgin  . 
3  lamps. 

7 
Gramme. 
3  lamps. 

8 
Gramme. 
5  lamps. 

9 

Siemens. 
5  lamps. 

10 
Weston. 
10  lamps 

11 
Brush. 
16  lamps 

12 
Brush. 
40  lamps 

13 
Brush. 
38  lamps 

1,017 

4-07 

737 
4-44 

1,380 
5-31 

1,535 
5-32 

1,695 
8-11 

1,496 
8-00 

826 
5-05 

1,003 
13-01 

770 
13-39 

700 
29-96 

705 
33-35 

0-70 
0-25 
0-95 
33-0 
63-0 

0'66 
0-12 
0'78 
36-0 

53-0 

1-68 
0-13 
1-81 
26-2 
44-5 

2-80 
1-50 
4-30 
18-5 
41-0 

0-52 
1-25 
1-77 
19-0 
63-0 

4-57 
0-62 
5-19 
15-3 
498 

7'05 
4-50 
11-55 

10-0 

47-4 

1-88 
1-50 
3-38 
23-0 
32-0 

10-55 
2-56 
13-11 

10-00 

44-3 

22-38 
2-60 
24-98 
9-5 
44-3 

22-38 
7-90 
3028 
9-5 
44-3 

1-41 

1-29 

1-69 

2'00 

0-87 

1-65 

1-57 

2-43 

1-79 

3-07 

3-72 

2-37 

2-52 

1-59 

1-027 

1-369 

1-04 

0-64 

1-00 

0-60 

0-573 

0-573 

2-31 
3-72 
84 

2-52 

3-81 
80 

3-18 
4-87 
136 

3-03 

5-08 
203 

4-11 
4-98 
193 

5-20 
6-85 
328 

3-20 

4-77 
353 

10-00 
12-43 
398 

9-60 
11-39 

840 

21-88 
24-95 
2,009 

20-79 
24-51 
1,971 

12 
246 
465 
239 
239 

18 
210 
805 
306 
306 

14 
142 

537 
205 
410 

13 

50 
227- 
82 
246 

14 
155 

357 
167 
501 

12 
112 
184 
102 
510 

10 
67 

72 
52 
260 

9  &  10 
92 
154 

85 
850 

11 

37 
76 
38 
608 

11 
63 
78 
39 
1,560 

11 
63 
78 
39 
1,482 

0-91 

0-86 

0-92 

0-95 

062 

0-86 

0-94 

0-95 

0-85 

0-83 

0-73 

0-57 

0-57 

0-60 

0-58 

0-51 

0-65 

0-63 

0-77 

0-72 

0-73 

0-62 

0-62 

0-66 

0-65 

0-61 

0-83 

0-76 

0-67 

0-80 

0-84 

0-87 

0-85 

58-7 

68-9 

77-2 

46-2 

61-8 

63'8 

51-5 

65-3 

45-4 

52-1 

44-4 

64-2 

80-3 

84-2 

48-4 

100-4 

74-5 

54-6 

68-4 

53-4 

62-6 

60-5 

103-5 

121-4 

129-3 

79-9 

121-6 

98-1 

81-3 

85-0 

63-3 

71-7 

71-4 

7-24 

8-74 

782 

4-43 

8-79 

6-67 

5-20 

3-70 

3-80 

4-11 

4-11 

308  PRODUCTION  OF  ELECTRIC   CURRENTS. 

eels  per  horse-power  applied  to  the  generator  shows  the  com- 
mercial value  of  the  different  sets  of  apparatus  as  a  whole 
for  lighting,  while  the  economy  of  the  lamps  by  themselves 
is  given  by  the  u  carcels  per  horse-power  of  energy  appearing 
in  the  arcs."  Aside  from  showing  in  a  general  way  that  the 
economy  of  a  lamp  is  greater  in  large  than  in  small  lights, 
there  is  not  much  to  be  learned  from  these  figures  of  the  rela- 
tive importance  of  the  various  factors  upon  which  the  light 
depends.  The  Siemens  (9)  and  the  Brush  (11,  12,  13),  which 
are  the  only  long-arc  lamps,  appear  to  indicate  a  superior 
economy  for  such  lamps,  as  the  former  gives  81  *3  carcels  per 
electrical  horse-power  appearing  in  the  arc,  in  lights  of  52 
carcels,  while  the  Brush  yields  71  carcels  in  lights  of  but 
39  carcels.  The  best  of  the  short-arc  lights  shows  85  carcels 
per  electrical  horse-power  in  the  arc,  in  lights  of  this  candle- 
power  (85  carcels).  Such  a  comparison  to  be  of  value,  how- 
ever, should  be  made  between  lights  of  the  same  candle- 
power,  or  on  the  basis  of  the  same  expenditure  of  energy  in 
the  arcs. 

The  Edison  machine  has  been  very  frequently  meas- 
ured, but  it  will  be  sufficient  to  give  here  two  tests — one 
made  by  Mr.  John  W.  Howell  at  the  Stevens  Institute,  and 
the  other  by  the  committee  of  the  Munich  Exhibition  of 
1882. 

In  the  former  the  electric  energy  developed  in  the  circuit 
was  determined  by  three  methods.  In  the  first,  the  current 
flowing  was  measured  by  means  of  a  voltameter,  or  copper 
depositing- cell.  This  test  is  made  by  determining  the  amount 
of  copper  carried  over  from  one  plate  of  the  cell  to  the  other 
in  a  given  time,  from  which  the  current  is  readily  determined, 
as  ,a  current  of  one  ampere  deposits  *32456  milligramme  per 
second.  The  electric  energy  in  the  circuit  is  then  given  by 
the  product  of  the  square  of  the  current  by  the  resistance 
(C2  H).  The  second  method  consisted  in  determining  the  cur- 
rent by  means  of  the  calorimeter — that  is,  by  finding  the  heat 
generated  by  the  current  in  a  coil  of  wire  of  known  resistance 
in  a  given  time.  This  heat  is  measured  by  immersing  the 
coil  in  a  definite  weight  of  water  and  noting  its  increase  of 
temperature.  The  energy  in  the  circuit  is  then  found  as  in 
the  first  method.  The  voltameter  and  calorimeter  were  each 
placed  in  the  circuit,  so  that  the  whole  current  passed  through 
them.  This  was  accomplished  by  taking  the  shunt  field- cir- 


MEASUREMENTS   OF  DYNAMOS  AND  ARC-LAMPS.         309 

cuit,  not  directly  from  the  brushes,  but  from  the  main  circuit 
beyond  the  point  at  which  the  measuring-cells  were  placed. 
The  third  method  consisted  in  measuring  the  electro-motive 
force  and  the  resistance,  the  energy  in  the  circuit  then  being 

E2  E 

— ,  which  is  equivalent  to  C  E.  since  C  =  — .     The  external 

K.  K, 

circuit  consisted  of  iron  wire  of  the  normal  resistance  of  the 
number  of  lamps  for  which  the  machine  was  designed,  to- 
gether with  the  copper  leads  to  be  used  with  them.  The 
mechanical  energy  applied  to  the  pulley  of  the  dynamo  was 
measured  by  a  pendulum  dynamometer  built  at  the  Insti- 
tute, and  every  care  was  taken  to  have  its  indications  correct. 
With  a  dynamometer  of  this  kind,  the  power  transmitted 
is  proportional  to  the  angle  through  which  the  pendulum — 
which  hangs  perpendicular  in  its  normal  position — is  lifted. 
The  instrument  was  standardized  by  determining  the  force 
which,  acting  at  the  circumference  of  the  dynamometer-pulley 
(one  foot  radius),  would  hold  the  pendulum  horizontal.  This 
was  found  to  be  171  '2  pounds ;  the  intensity  of  any  other 
force  would  therefore  be  given  by  multiplying  this  by  the 
sine  of  the  angle  through  which  the  pendulum  was  raised. 
To  get  the  work  done  per  minute,  or  the  power,  it  is  neces- 
sary to  multiply  this  force  by  the  distance  traveled  by  the 
pulley.  This  is,  of  course,  the  product  of  the  number  of 
revolutions  by  the  length  of  the  circumference  in  feet.  As 
the  radius  of  the  pulley  is  one  foot,  the  travel  is  equal  to  the 
number  of  revolutions  multiplied  by  6 '2832.  The  total  power 
transmitted  by  the  dynamometer  included  that  required  to 
overcome  the  friction  of  both  the  dynamometer  and  the  arma- 
ture of  the  dynamo.  These  combined  frictions  were  found  to 
equal  13£  per  cent  of  the  power  transmitted,  while  that  of  the 
dynamometer  was  equivalent  to  10 '9  per  cent.  The  net  power 
applied  to  the  armature  is  obtained,  therefore,  by  multiplying 
the  total  power  transmitted  by  '865,  and  the  gross  applied 
power  by  multiplying  the  transmitted  power  by  '891.  The 
data  and  the  results  obtained  by  these  tests  are  given  below : 

DATA  OBTAINED  FKOM  VOLTAMETER  TEST. 

Weight  of  copper  gained  by  negative  plates  =  24,465  milli- 
grammes. 

Time  of  test  =  fifteen  minutes. 


310  PRODUCTION   OF  ELECTRIC   CURRENTS. 

Weight  gained  per  second  =  27  '183  milligrammes. 

Average  speed  of  dynamometer  =  400*5  revolutions  per 
minute. 

Average  deflection  of  pendulum  =  42°  20'.  (sine  =  '67344) 

Resistance  of  iron  wire  =  '76  ohm. 

Resistance  of  iron  wires  and  magnet  coils  in  multiple  arc 
—  "744  ohm. 

Total  resistance  of  circuit  =  '744  +  .029  —  .773  ohm. 

Internal  resistance  of  armature  =  '016  ohm. 

RESULTS  OBTAINED  FROM  DATA. 

27*183 
Yalue  of  current  in  amperes  ==  =  83*753. 

* 


Electrical  energy  =  (83'753)2  x  *773  x  44*24*  =  239880*726 
foot-pounds  per  minute. 

Energy  indicated  by  dynamometer  =  171  '2  x  *67344  x  400  '5 
x  6-2832  =  290125*54  foot-pounds  per  minute. 

Friction  of  dynamometer  and  generator  =  290125*54  x  *135 
=  39166-9479  foot-pounds  per  minute. 

Energy  used  in  turning  armature  in  field  of  force  =290125*54 
x  *865  =  250958*59  foot-pounds  per  minute. 

Friction  of  dynamometer  alone  =  290125*5  x  *109  =  31623*68 
foot-pounds  per  minute. 

Energy  actually  applied  to  armature  pulley  =  290125*54  x 
•891  =  258501*96  foot-pounds  per  minute. 


Of  the  total  electrical  energy,  239880*7--^  =  4965*189  ap- 

/  /  o 

•744 

peared  in  the  armature,  -  -  x  239880*726  =  4647*39 

*773  x  49*68 

in  the  magnet  coils,  and  230268*176  foot-pounds  per  minute  in 
the  external  circuit. 

The  efficiency  of  the  generator  is  the  ratio  of  the  energy 
required  to  turn  the  armature  in  the  magnetic  field,  to  the 

,       239880*726 

total  electrical  energy  developed  =  =  *955. 

* 


The   commercial   efficiency    is    the   ratio   of  the   energy 
required  to   drive  the  machine  (including  friction)  to  the 

*  This  is  the  factor  for  converting  watts  into  foot-pounds  per  minute:  a 
watt  =  —  —  horse-power,  =  -  ,  =  44'24  foot-pounds  per  minute. 


MEASUREMENTS   OF  DYNAMOS  AND  ARC-LAMPS.         311 

electrical  energy  which  appears  in  the  external  circuit  = 
230268-169 
258501-96  ^ 

DATA  OBTAINED  FROM  CALORIMETER  TEST. 

Water  in  calorimeter  =  77  pounds. 
Correction  for  waste  heat  =  1  '78  pound. 
Kange  of  temperature  =  97°  —  69*8°  =  9  '2°  F. 
Specific  heat  for  this  range  =  1-0015. 

Average  speed  of  dynamometer  =  394  revolutions  per 
minute. 

Average  deflection  of  pendulum  =  43°  24'  (sine  =  '68709). 
Time  of  test  =  sixteen  minutes. 

Resistance  of  iron  wires  and  calorimeter  coil  =  *68  ohm. 
This  and  magnet  coil  in  multiple  arc  =  '667  ohm. 
Total  resistance  of  circuit  =  '667  +  '029  =  '696  ohm. 
Resistance  of  calorimeter  coil  =  '1  ohm. 

RESULTS  OBTAINED  FROM  THESE  DATA. 

78  -78x1  -0015x9  -2x772 
Energy  developed  in  calorimeter  =  - 

lo 

=  35022*897  foot-pounds  per  minute. 

Total  electrical  energy  =35022  '897  x  6  '96  =  243759-36  foot- 
pounds per  minute. 

Energy  indicated  by  dynamometer  =  171  '2  x  -68709  x  394 
x  6  '2832  =  291201-46  foot-pounds  per  minute. 

Energy  used  in  turning  armature  in  field  of  force  =291201  -46 
x  -865  =  251889-265  foot-pounds  per  minute. 

Energy  actually  applied  to  armature  pulley  =  291201*46 
x  -891  —  259460-5  foot-pounds  per  minute. 

*rv-|  ft 

Of  the  electrical  energy,  243759*36  x  -    -  =  5603.66  ap- 

*o9o 

•  &B.l*f 

peared  in  the  armature,  243759*36  x  -—-  7^—7  =  4215*89  in 

x  oo  41 


the  magnet  coils,  and  233939*81  foot-pounds  per  minute  ap 
peared  outside. 

243759*363 

251889^5 

233939*81 

Commercial  efficiency  =  =  -901. 

* 


312  PRODUCTION  OF  ELECTRIC  CURRENTS. 

DATA  OBTAINED  FROM  MEASUREMENT  OF  ELECTRO-MOTIVE 
FORCE  AND  RESISTANCE. 

Electro-motive  force  =  53  volts. 
Resistance  of  circuit  (external)  =  '64  ohm. 
Resistance  between  binding-posts  =  '629  ohm. 
Average  speed    of   dynamometer  =  355  revolutions    per 
minute. 

Average  deflection  =  42°  (nat.  sine  =  -66913). 
Total  resistance  of  circuit  =  '658  ohm. 

RESULTS  OBTAINED  FROM  THESE  DATA. 

Energy  developed    in    external  circuit  -t  —  -    x   44  '24  = 

* 


197567*43  foot-pounds  per  minute. 

Total  electrical  energy  ='197667-43  x  —  -  =  206673-0295 

* 

foot-pounds  per  minute. 

Energy  in    armature  =  206673*029  x  7—  =  5025*5   foot- 

uOo 

pounds  per  minute. 

Energy    in    magnet    coils  =  \  —  '  x  44  -24  =  3358  '6   foot- 

o7 

pounds  per  minute. 

Energy  in  external  circuit  —  198288*8  foot-pounds  per 
minute. 

Energy  indicated  by  dynamometer  171*2  x  *66913  x  355  x 
6-2832  =  255519-04  foot-pounds  per  minute. 

Energy  used  in  turning  armature  in  field  of  force  255519*04 
x  *865  =  221023-97  foot-pounds  per  minute. 

Energy  actually  applied  to  armature  pulley  255519*04  x 
•891  =  227667*47  foot-pounds  per  minute. 

T™  .  206673-0295 

Efficiency  =  --r  =  '935. 


n  .  ,     ~  .  198288-8 

Commercial  efficiency  =  =:  *87- 


Average  efficiency,  *951. 

Average  commercial  efficiency,  '887. 

The  Munich  committee  examined  three  sizes  of  the  Edison 
machine  —  those  for  250,  60,  and  17  lamps  —  but  it  will  be  suffi- 
cient to  give  the  tests  of  the  60-lamp  machine.  The  experi- 


MEASUREMENTS   OF  DYNAMOS   AND  ARC-LAMPS. 


menters  explain  that  the  low  " practical  generative  efficiency" 

— ,  and  the  " commercial  efficiency"  — ,  are  accounted  for  by 
.A.  -A. 

the  stiffness  of  the  driving-belt,  the  power  required  to  drive 
the  machine  when  it  was  doing  no  electrical  work  being  2*19 
horse-power.  Subtracting  this  from  the  total  power,  A,  ap- 
plied to  the  dynamo,  we  have  for  the  " generative  efficiency" 

in  the  six  cases  in  the  table,  - — -— =  82 '3,  85*5,  84 '9,  86  '2, 

-£i- — <^*-Ly 

87 '4,  87 '4,  and  for  the  relation  between  the  net  horse-power 

and  electrical  energy  in  the  external  circuit,  - — — —  =  71  *2, 

A. — a'!.*) 

74-4,  73-9,  75-4,  76 '6,  76.8. 

Examination  of  the  Edison  Dynamo 

BY     THE     COMMITTEE     OF     THE     MUNICH     EXHIBITION     OF     1882. 


MACHINE  USED. 

RESISTANCE 
WARM 

(OHMS). 

t 

i 
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ty  of  current  in  the 
•nal  circuit,  I  (am- 

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INTKNSITY 

OF  CURRENT 
(AMPERES). 

« 

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ectro-moti  ve  force, 
>lts). 

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B 

111 

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•166 

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40-7 

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3-96 

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31-42 

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ELECTRICAL   WORK. 

s 

, 

RESULTS. 

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EXTERIOR 
CIRCUIT,  1. 

ARMATURE. 

FIELD. 

TOTAL,  L. 

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BOOK    Y. 
DISTRIBUTION    OF    ELECTRICITY. 


CHAPTER  I. 

FIRST  MODE  OF  DISTRIBUTION. 

IT  is  electric  lighting  which  has  had  to  solve  the  problem 
of  the  distribution  of  electricity.  At  first  the  most  powerful 
center  of  light  possible  was  sought  for,  by  concentrating  on 
one  given  point  the  highest  intensity  of  current ;  when  the 
first  practical  application  of  it  came  to  be  tried,  it  was  evident 
that  these  concentrated  masses  of  light  did  not  meet  all  the 
necessities  of  the  case  ;  that  in  the  greater  number  of  cases  a 
light,  weaker  perhaps  in  total  intensity,  but  better  distrib- 
uted, would  be  preferable ;  finally,  that  it  was  necessary  to  in- 
crease the  number  of  lights,  even  at  the  risk  of  reducing  their 
brightness. 

But  all  this  was  not  unaccompanied  by  difficulties :  as  the 
question  at  this  time  was  simply  how  a  very  limited  number 
of  lamps  were  to  be  made  to  work  at  the  same  time,  attention 
was  devoted  to  the  lamp  itself  ;  this  first  question  was  solved, 
as  we  have  stated,  by  the  derived-circuit  lamps.  Scarcely  was 
this  answer  obtained,  when  it  was  found  incomplete,  and  the 
endeavor  was,  not  only  to  place  several  lamps  upon  the  same 
circuit,  but  to  derive  even  several  circuits  from  one  machine. 
Had  this  problem  been  attacked  directly,  it  would  have 
amounted  to  the  very  question  of  the  division  of  the  current. 
At  the  period  alluded  to,  about  1872,  it  was  far  from  ripe  ;  it 
was  evaded,  and,  instead  of  dividing  the  electric  current  as  it 
left  the  machine,  the  machine  itself  was  divided. 


FIRST  MODE  OF  DISTRIBUTION.  315 

I.   ELECTRIC  CONDUCTORS. 

The  first  machine  which  had  given  a  practical  electric 
light,  the  Alliance  machine,  had  already  furnished  an  example 
of  this  method,  and  naturally  pointed  out  this  way  ;  it  is,  as 
we  have  seen,  composed  of  a  series  of  bobbins  placed  circu- 
larly on  wooden  disks  ;  each  of  these  disks  constitutes  a  com- 
plete machine,  and  can  work  independently.  It  was  not  long 
before  it  was  known  how  to  separate  them  so  as  to  form  in- 
dependent circuits  connected  with  different  apparatus ;  the 
alternating-current  machine  of  Lontin  by  different  means  at- 
tained the  same  result ;  the  armature  bobbins,  fixed  in  place, 
were  coupled  in  separate  series,  each  devoted  to  supplying  a 
circuit  of  its  own  ;  a  similar  arrangement  was  adopted  in  the 
Gramme  alternating-current  machine,  where  the  sections  of  the 
armature  ring  were  separated  so  as  to  work  independently. 

These  methods  did  not  amount  to  the  true  distribution  of 
light ;  nevertheless,  they  are  the  only  ones  which  have  been 
employed  in  the  last  few  years.  Before  the  Exhibition  of 
1881  no  other  methods  had  been  seen  in  genuine  practical 
working,  and  it  is  with  these  very  limited  means  that  the  im- 
portant applications  known  to  all  the  world  have  been  made. 

These  works,  however,  have  led  to  complete  and  interest- 
ing studies  on  conductors,  and  the  method  of  arranging  them ; 
these  results  do  not  depend  on  the  method  of  division  em- 
ployed, and  are  obtained  from  theory ;  it  will  be  useful  to 
devote  a  few  lines  to  them. 

All  conductors  hitherto  employed  are  of  copper ;  of  all 
good  conducting  metals  it  is  the  only  one  whose  price  is 
reasonable  ;  iron  is  cheaper,  it  is  true,  for  equal  conductivity, 
but,  when  currents  of  a  certain  intensity  have  to  be  passed, 
its  use  renders  so  large  a  conductor  necessary  that  the  wire 
ceases  to  be  manageable,  and  necessitates  repeated  solderings, 
which  would  compensate,  and  more,  for  the  low  price  of  the 
iron. 

There  would  be  a  certain  advantage  in  using  an  uncovered 
wire  suspended  in  the  air :  the  cooling  would  be  easier.  But 
in  practice  this  arrangement  meets  with  many  obstacles.  A 
wire  suspended  in  the  open  air  is  liable  to  many  accidents ; 
dampness  occasions  loss  of  current  by  the  supports — losses 
which,  annoying  even  with  the  weak  telegraphic  currents, 
would  be  intolerable  with  the  strong  currents  used  for  the 


316  DISTRIBUTION  OF  ELECTRICITY. 

electric  light.  Thus,  as  a  rule,  the  conductors  are  necessarily 
placed  underground,  and  are  properly  insulated. 

The  section  of  the  conductor  varies  naturally  with  the  in- 
tensity of  the  current.  It  should  be  large  enough  to  avoid 
all  sensible  heating ;  but  as  in  reality  the  resistance  of  the 
conductor  can  not  be  reduced  to  zero,  the  passage  of  the  cur- 
rent always  causes  heating.  The  question  then  arises  of  where 
the  saving  is  to  be :  on  one  side  are  the  interest  and  depre- 
ciation to  be  charged  against  the  cost  of  putting  up  the  con- 
ductor ;  on  the  other  side  the  cost  of  the  electricity  which  is 
wasted  in  heating  the  wire  by  its  passage.  This  last  expense 
is  incurred  -only  during  the  working  periods  of  the  system ; 
the  length  of  these  periods  of  lighting  must  then  be  taken 
into  account  in  these  calculations.  In  cases  where  the  con- 
ductor is  of  large  diameter,  instead  of  using  a  conductor 
formed  of  a  single  large  rod  of  metal,  a  cable  formed  of  sev- 
eral wires  united  and  lightly  twisted  together  is  adopted. 
These  cables  are  more  flexible  than  a  single  heavy  wire,  are 
more  easily  placed,  and  are  less  liable  to  break,  the  wires 
rarely  all  breaking  at  one  and  the  same  place. 

The  conducting  wires  are  covered  with  silk  or  cotton, 
braided  by  a  machine  ;  sometimes  gutta-percha  is  employed. 
If  a  cable  is  in  question,  it  is  wrapped  with  silk  bands  im- 
pregnated with  coal-tar,  or  with  India-rubber  bands ;  some- 
times it  is  passed  through  a  regular  India-rubber  tube ;  the 
cables  used  in  the  Jablochkoff  system  are  thus  insulated.  If 
the  conductors  are  placed  in  very  wet  situations,  they  are 
covered  with  leaden  tubes  ;  this,  for  example,  has  been  done 
with  the  telephone  wires  that  pass  through  the  Parisian  sew- 
ers ;  the  cables  running  under  the  pavement  of  the  Place  du 
Carrousel  were  made  in  this  manner  also. 

When  a  water  or  gas  main  is  laid  it  is  tested  throughout 
its  length  for  obstructions  or  leaks  ;  in  the  same  way,  when 
one  of  these  large  conductors  is  laid,  its  good  working  has 
to  be  tested  with  exact  instruments  ;  not  only  must  the  cur- 
rent pass,  but  it  must  pass  with  the  requisite  intensity;  for 
this  reason  the  cable  is  tested  to  see  if  it  has  the  normal  re- 
sistance, and  if  there  is  no  loss  of  electricity  in  its  course 
through  it. 

Further  on  we  shall  see  interesting  systems  of  canalization 
for  the  most  complete  distribution  ;  but  so  far  they  have  not 
been  applied.  The  means  which  we  are  about  to  briefly  de- 


FIRST  MODE   OF  DISTRIBUTION".  317 

scribe  have,  on  the  contrary,  rendered  great  service ;  they 
have  been  used  for  important  installations  of  light  that  were 
relatively  quite  different  in  their  conditions. 

The  two  extremes  are,  without  doubt,  on  the  one  hand 
lighting  with  ordinary  regulators,  such  as  those  established 
by  M.  Jaspar,  in  which  each  lamp  has  it&  machine  ;  and, 
on  the  other  hand  the  Brush  system  of  lighting,  where  as 
many  as  thirty-four  lamps  have  been  placed  on  a  circuit  over 
six  kilometres  long.  One  can  not  help  thinking  that  both 
systems  have  their  weak  points.  The  first,  a  very  simple  one, 
is  very  costly  in  its  plant ;  the  second,  although  it  has  gen- 
erally given  good  results,  evidently  puts  the  apparatus  in 
a  condition  of  reciprocal  dependence  that  is  a  source  of 
danger.  A  medium  course  is  probably  the  best,  and,  as  in 
systems  employing  divided-current  machines,  distinct  circuits 
maybe  adopted,  each  one  carrying  a  reasonable  number  of 
lamps. 

We  will  describe  as  an  example  the  lighting  of  the  port  of 
Havre  by  means  of  the  Jablochkoff  candle,  a  plant  recently  put 
in  place,  and  which  comprises  almost  all  the  improvements 
which  this  method  of  dividing  the  light  is  susceptible  of. 


II.  DISPOSITION  OF  ELECTRIC  WIRES  FOR  LIGHTING  THE 
PORT  OF  HAVRE. 

The  port  of  Havre,  as  is  known,  is  a  sea-port,  and  large 
vessels  can  only  enter  it  at  high  tide.  When  both  high  tides 
come  at  day-time,  vessels  which  miss  the  first  can  enter  by 
the  second  tide,  and  consequently  have  only  eleven  hours  to 
lay  in  the  roads ;  but,  when  the  tides  come  one  in  the  day 
and  one  at  night,  the  ship  which  missed  the  day-tide  could 
not,  up  to  the  present  time,  enter  the  port  before  the  following 
day ;  sometimes  it  had  to  remain  twenty-four  hours  in  the 
roads.  The  anchorage  at  Havre  is  excellent  for  vessels  to  lay 
at  in  calm  weather,  but,  when  it  blows,  the  anchor  must  be 
lifted.  The  transatlantic  steamers  know  something  of  this, 
and  several  steamers  have  been  cited  this  winter  that  were 
forced  to  go  to  Cherbourg  to  land  their  passengers. 

This  was  the  source  of  the  strong  desire  mariners  had  to 
be  able  to  enter  the  port  of  Havre  by  night  as  by  day,  and  it 
was  at  their  request  that  the  city  authorities  decided  to  light 
the  port  by  electric  light.  This  decision  was  reached  in  the 


FIRST  MODE   OF  DISTRIBUTION.  319 

year  1880,  but  it  is  only  since  the  beginning  of  the  year  1881 
that  the  lighting  has  been  in  operation. 

Whenever  there  is  a  night-tide  the  jetties,  breakwater,  and 
principal  dock  are  lighted  an  hour  before  and  two  hours 
after  the  period  of  the  full  tide,  and  large  ships  can  enter 
just  as  by  daylight. 

The  installation  comprises  thirty-four  lamps,  thirty-two  of 
which  are  shown  on  the  plan  in  Fig.  197 ;  two  others  were 
added  after  this  plan  was  laid  out,  and  the  machines  em- 
ployed have  capacity  to  supply  forty. 

'  These  thirty-two  lights  are  placed  on  six  circuits.  The 
first  circuit  of  four  lamps  (1  to  4)  lights  the  north  jetty  ;  it  is 
3,900  metres  long,  going  and  coming.  The  second  circuit  of 
five  lamps  (5  to  9)  lights  the  large  quay,  it  measures  2,900 
metres  ;  a  sixth  lamp  has  been  added  to  it,  placed  in  a  red  lan- 
tern and  serving  as  a  guide  to  steer  by.  The  third  circuit  of 
six  lamps  (10  to  15)  comprises  the  Notre-Dame  and  De  la  Barre 
docks ;  it  is  1,900  metres  long.  The  fourth  circuit  of  six 
lamps  (16  to  21)  lights  the  lower  end  ;  it  includes  a  red  light, 
and  measures  1,250  metres.  The  fifth  circuit  of  six  lights  (22 
to  27)  lights  the  dock  of  the  transatlantic  and  those  of  the 
Florida  steamers  ;  it  is  1,400  metres  long.  The  sixth  circuit 
of  five  lamps  (28  to  32)  lights  the  south  jetty ;  it  measures 
2,900  metres,  and  has  a  red  light. 

The  machines  are  installed  not  far  from  the  transatlantic 
dock.  Two  steam-engines  of  thirty-five  horse-power  each 
drive  four  self-exciting  Gramme  machines  of  type  2.  One  of 
these  four  Gramme  machines  works  on  open  circuit ;  it  is 
only  intended  for  use  when  an  accident  happens  to  one  of  the 
three  others.  Each  of  the  others  supplies  two  circuits.  As  all 
the  circuits  are  similarly  arranged,  we  shall  only  consider  the 
working  of  one  of  them. 

It  is  shown  in  the  annexed  diagram  (Fig.  198),  in  which 
the  proportion  of  parts  has  not  been  preserved,  but  which  is 
only  designed  to  indicate  their  respective  positions. 

M  is  the  self -exciting  Gramme  machine,  supplying  the  two 
circuits  C  and  C',  of  which  we  shall  only  consider  the  first. 

The  current  of  this  machine  is,  to  begin  with,  susceptible 
of  a  certain  regulation  by  means  of  a  resistance,  R,  connected 
with  the  terminals  B  and  B'.  This  apparatus  is  placed  between 
the  exciting-machine  and  field  of  the  generator,  so  that  by 
changing  the  resistance  the  intensity  of  the  magnetic  field 

22 


FIRST  MODE  OF  DISTRIBUTION.  321 

can  be  made  to  vary,  and  the  current  produced  can  thus  be 
regulated. 

The  conductors  forming  the  circuit  C,  under  consideration, 
first  reach  two  handles,  P  and  P',  terminated  by  metallic 
pieces  that  go  into  metallic  sockets,  G  and  G',  fastened  on 
the  wooden  base,  E.  The  object  of  this  arrangement  is  the 
following :  If  any  accident  happens  to  the  machine,  the  han- 
dles, P  P',  are  lifted  and  replaced  by  two  other  similar  ones 
that  receive  the  wires  from  the  reserve  machine,  so  that  the 
current  will  not  be  interrupted  but  for  a  very  short  period. 

In  the  course  of  the  conductor,  L,  as  it  leaves  G,  a  resist- 
ance-frame is  placed,  designed  to  render  the  current  through 
the  circuit  C  equal  to  that  through  the  other  circuit  C'  of  the 
machine.  The  unequal  intensity  of  these  two  currents  is  due 
to  two  causes :  first,  to  the  inequality  of  length  of  the  cir- 
cuits, and  consequently  of  resistance,  secondly,  to  this  fact, 
proved  by  experience,  that  in  the  self-exciting  machine  the 
circuit  C,  that  is  nearest  to  the  exciter,  has  a  higher  electro- 
motive force  produced  in  it  than  the  other.  The  frame,  S, 
makes  both  currents  equal. 

The  conductor,  L,  next  reaches  at  H  a  double-contact 
switch.  The  two  conductors,  I/  and  L",  which  leave  H,  run 
out  of  the  engine-room,  and  carry  the  current  to  the  lamps  F, 
F,  F  ;  they  return  by  the  wire  L'. 

Before  returning  to  G',  this  return  circuit  passes  through 
an  electro-magnet,  A,  which,  during  the  passage  of  the  cur- 
rent, holds  an  armature,  D,  constantly  attracted.  If  an  ex- 
tinction be  produced  in  any  lamp,  the  current  ceases  to  pass  ; 
the  armature,  as  it  separates,  closes  the  contact,  K,  and  sounds 
an  alarm-bell,  T  ;  this  gives  the  warning,  and,  as  we  shall  see, 
the  relighting  can  be  immediately  effected. 

As  we  have  seen  already,  most  of  the  circuits  contain  six 
lamps ;  in  our  diagram,  for  the  sake  of  simplicity,  we  have 
only  shown  three.  All  these  lamps  hold  four  Jablochkoff 
candles,  with  six  millimetre  carbons ;  but  the  first  ones  con- 
tain each  two  candle-holders  with  two  candles  each,  and  have 
consequently  two  return  wires  ;  the  last,  on  the  contrary,  con- 
tains a  four  candle-holder,  of  the  ordinary  form,  with  a  single 
return  wire.  Finally,  in  the  foot  of  each  candelabrum  is 
placed  a  switch-board,  O  (X,  of  six  plates,  through  which  the 
current  passes  before  reaching  the  lamp. 

This  arrangement,  apparently  complicated,  attains  two  re- 


322  DISTRIBUTION  OF  ELECTRICITY. 

suits :  first,  in  normal  working,  without  leaving  the  engine- 
room,  the  superintendent  can  cause  the  current  to  pass  from 
the  candles  1  to  the  candles  2,  by  means  of  the  switch  H  ;  in 
the  second  place,  in  case  of  extinction,  after  having  replaced 
the  candles  I  by  candles  2,  he  can  prepare,  by  simple  manipu- 
lation of  the  switches,  O  O',  the  candles  3  for  a  fresh  passage 
of  the  current. 

To  understand  how  this  is  effected,  let  us  first  suppose  the 
switch  H  so  placed  that  the  current  follows  the  conductor 
L" :  it  first  reaches  the  upper  left-hand  piece  of  the  switch- 
board O  (X  of  the  first  lamp-post ;  thence  it  goes  to  the  candle 
1 ;  following  then  the  return  wire  from  the  lamp  1-3,  it  reaches 
the  middle  piece  on  the  same  side,  and  leaves  that  for  the 
switch  of  the  second  lamp-post.  In  this  as  in  the  rest  the 
current  takes  the  same  course,  and  it  is  the  same  in  the  last, 
with  this  exception,  that  there  is  one  return  wire  only  ;  finally, 
the  current  returns  to  the  machine  by  the  wire  L',  passing 
through  the  electro-magnet  A. 

In  this  course  it  will  be  seen  that  the  current  follows  the  full 
lines  of  the  diagram.  If,  now,  when  the  candles  1  are  burned 
up,  the  switch  H  be  changed,  so  that  the  current  traverses  L", 
it  will  follow  a  course  absolutely  symmetrical  with  the  first  one, 
indicated  by  the  dotted  lines,  and  will  supply  the  candles  2. 
The  return  will  take  place  as  before,  through  the  wire  I/.  At 
present,  suppose  that  the  current  coming  through  L"  (full  lines) 
and  lighting  the  candles  1,  a  sudden  extinction  takes  place, 
notice  of  it,  in  the  engine-room,  will  be  given  by  the  bell  T ;  the 
first  thing  to  be  done  will  be  to  place  the  switch  H  upon  L'", 
which  will  light  all  the  candles  2,  so  that  the  lighting  will  have 
no  interruption  of  any  considerable  length.  Then  each  lamp- 
post must  be  visited,  and  the  hole  that  separates  the  two  up- 
per pieces  of  its  switch-board  must  be  closed  with  a  screw- 
plug  ;  the  right-hand  piece  communicating,  as  we  have  seen  in 
the  drawing,  with  the  candle  3,  it  follows  that  after  this  new  ar- 
rangement of  the  switch-board  O  O',  if,  at  the  moment  the  can- 
dles 2  are  burned,  the  switch  of  H  be  again  pressed  upon  the 
conductor  L",  the  current  will  pass  through  all  the  candles  3. 

If,  then,  following  this  out,  the  lower  pieces  of  the  switch- 
board at  O'  be  connected,  as  the  left  hand  is  in  relation  to  the 
candle  4,  a  new  change  of  the  switch  H  will  light  all  the 
candles  4. 

Thus,  in  a  single  evening  all  four  candles  of  the  same  lamp 


FIRST  MODE   OF  DISTRIBUTION. 


can  be  lighted.  But  in  Havre  this  is  never  necessary ;  the 
illumination  lasts  only  three  hours,  so  that  two  candles  are 
quite  sufficient,  and  in  normal  operation  the  current  is  shifted 
from  one  candle  to  the  other  by  the  attendant  in  the  engine- 
room.  The  arrangement  we  have  just  described  is  only  of 
value  in  case  of  an  accident. 

In  each  of  the  switch-boards  of  the  lamp-posts,  the  upper 
left-hand  piece  and  the  lower  right-hand  piece  can  be  con- 
nected by  a  screw-plug  each  one  with  the  corresponding  mid- 
dle piece.  These  two  connections  are  for  the  purpose  of  cut- 
ting out  the  lamp  from  the  circuit,  whether  the  current  passes 
through  L"  or  L'". 

The  arrangement  of  the  six  circuits  is  similar  to  that  which 
we  have  described  :  all  the  wires  first  reach  the  beam  E  which 
supports  all  the  handles ;  the  electro-magnets  A  and  the 
switches  H,  marked  with  numerals  in  their  order,  are  arranged 
side  by  side  in  the  operating  or  engine-room,  so  that  the 
manipulation  is  thus  rendered  very  easy. 

All  the  conductors  go  out  together,  and  then  diverge 
toward  the  different  points  where  they  are  to  be  used. 

At  places  where  the  cables  must  be  fastened  together  un- 
derground it  is  desirable  to  avoid  splicing  and  to  provide  a 
means  of  control  and  repair ;  for  that  purpose  the  special 
arrangement  shown  in  section  in  Fig.  199  has  been  adopted. 

A  A  is  an  earthenware 
cylinder  about  fifty  cen- 
timetres high ;  it  is  placed 
underground,  and  the  two 
ends  of  the  cable  to  be 
united  are  passed  into  the 
box  through  its  lower  end 
and  bent  upward.  The 
cylinder  is  then  filled  to 
about  one  third  of  its 
height  with  thin  cement ; 
above  the  layer  of  cement 
the  cable  is  laid  bare,  and 
the  two  ends  united  by  a 

screw-coupling ;  the  whole  is  covered  with  a  layer  of  paraf- 
fine ;  the  cylinder  is  then  closed  with  cement.  Each  cylinder 
of  this  kind  contains  several  junctions  ;  the  number  varying, 
according  to  the  circumstances,  from  three  to  twelve.  A 


FIG.  199.— Junction-box. 


324  DISTRIBUTION   OF  ELECTRICITY. 

sheet-iron  cover  with  a  hole  through  its  middle,  and  laid  flush 
with  the  soil,  closes  the  cylinder.  When  the  junctions  are 
to  be  examined  this  plate  is  raised,  the  upper  layer  of  cement 
is  broken,  and  the  paraffine  is  thus  reached. 

The  engraving  (Fig.  200)  gives  an  idea  of  the  effect  pro- 
duced, and  enables  a  conception  to  be  formed  of  the  extent  of 
this  plant,  one  of  the  largest  and  most  carefully  laid  out  in 
existence. 


CHAPTER  II. 

CONDITIONS  OF  A   GENERAL  DISTRIBUTION. 

To  tell  the  truth,  in  all  the  installations  of  a  number  of 
lamps  which  we  are  describing,  the  problem  of  the  distribution 
of  the  light  is  more  often  studied  than  solved  ;  in  practice,  the 
generating  machine  is  divided  into  several  separate  genera- 
tors ;  on  each  of  the  circuits  thus  obtained  a  restricted  num- 
ber of  lamps,  self -regulating  within  a  certain  range,  is  placed ; 
moreover,  when  the  whole  is  once  in  position  and  adjusted, 
all  remains  in  the  same  state  during  the  period  of  action.  In 
a  genuine  distribution,  the  power  of  adding  or  removing  some 
lamps  must  exist,  without  disarranging  those  which  are  still 
working,  the  electrical  generator  furnishing  always  the  exact 
quantity  of  current  necessary  for  whatever  number  of  lamps 
may  be  working  at  the  time.  Under  these  conditions  variable 
quantities  of  work  must  be  produced,  according  to  the  de- 
mand, and  divided  according  to  the  needs,  which  may  be 
variable.  The  problem  is  then  infinitely  more  complicated. 

The  general  conditions  to  which  the  solution  must  conform 
may  be  now  understood.  A  generator  being  given,  there  are 
only  two  means  of  making  it  supply  several  electrical  appa- 
ratus :  the  first  is  to  place  them  in  succession,  one  after  the 
other,  on  a  single  circuit ;  the  second  is  to  arrange  them  singly 
or  in  groups  across  the  circuit :  in  the  first  case,  the  lamps 
are  said  to  be  either  in  series  or  in  tension  ;  in  the  second  case 
they  are  in  derivation,  quantity,  or  in  multiple  arc. 

A  comparison  will  render  sensible  the  difference  between 
the  two  arrangements.  Suppose  the  problem  is  to  utilize  a 
waterfall  by  causing  it  to  turn  several  water-wheels ;  these 
can  be  placed  one  below  the  other,  each  of  them  receiving  all 


FIG.  200. — View  of  the  port  of 


re  lighted  by  Jablochkoff  candles. 


CONDITIONS  OF  A   GENERAL  DISTRIBUTION.  325 

the  water  of  the  fall,  but  utilizing  only  a  part  of  its  height ; 
or  one  can  be  placed  beside  the  other,  each  of  them  utiliz- 
ing all  the  height  of  the  fall,  but  receiving  only  a  part  of  its 
water-supply.  In  the  first  case  the  apparatus  are  in  series, 
in  the  second  they  are  in  derivation. 

This  comparison  shows  us  how  the  two  systems  of  division 
can  work.  In  the  first  case,  the  fall  being  already  utilized,  if 
we  wish  to  introduce  a  new  water-wheel,  to  find  it  a  place,  it 
will  be  necessary  to  increase  the  height  of  the  fall,  the  volume 
of  the  river  remaining  the  same ;  in  the  second  case,  it  will 
be,  on  the  contrary,  the  volume  of  the  river  which  must  be 
increased  to  actuate  the  new  wheel,  the  height  of  the  fall  not 
needing  to  be  changed.  In  an  electric  system  it  may  be  said 
that,  with  the  arrangement  in  series  the  tension  can  be  changed 
without  changing  the  intensity,  while  with  the  arrangement 
in  derivation  the  tension  will  remain  constant,  the  intensity 
being  made  to  vary. 

In  all  cases  there  is  an  element  which  varies  according  to 
the  expenditure  of  electrical  energy  which  the  lighting  appa- 
ratus require.  It  will  always  be  necessary,  therefore,  for  vari- 
able conditions,  to  provide  a  system  adapted  for  regulation  of 
the  generator,  constantly  keeping  it  in  condition  to  furnish 
the  quantity  of  electricity  requisite  for  the  work.  This  ar- 
rangement is  indispensable  ;  it  can  only  be  suppressed  if  the 
source  of  electricity  could  be  reduced  to  a  simple  force  with- 
out material  organization  ;  in  this  case,  all  the  circuit  being  a 
useful  circuit,  the  production  would  naturally  become  pro- 
portional to  its  chance  of  escape.  But  this  result  is  impos- 
sible. The  generator  always  forms  a  portion  of  the  circuit, 
and  indeed  often  an  important  part ;  its  presence  implies  the 
necessity  of  a  regulating  organ,  without  which  it  is  impossible 
to  solve  fully  the  problem  of  distribution. 

The  worth  of  the  solution  of  the  problem  depends  on  the 
perfection  of  the  regulating  mechanism  which  it  involves, 
and  in  the  degree  of  perfection  with  which  it  fulfills  the  three 
following  conditions : 

1.  All  the  apparatus  placed  on  the  circuit  of  the  same 
electric  generator  must  work  independently  of  each  other. 

2.  The  regulation  which  should  be  exercised  over  the  gen- 
erator for  attaining  the  preceding  result  should  be  performed 
automatically  and  by  the  current  itself,  no  human  surveil- 
lance being  as  quick  and  as  exact  as  electricity. 


326  DISTRIBUTION   OF  ELECTRICITY. 

3.  The  regulation  should  be  managed  so  that  the  genera- 
tor, while  sufficing  for  variable  expenditures,  may  never  exact 
work  in  excess  of  the  expenditure,  so  that  there  is  no  loss. 

I.  REGULATORS  or  THE  INTENSITY  OF  CURRENTS. 

We  have  said  that  the  question  of  distribution  had  been 
propounded  after  the  serious  study  of  electricity.  As  long 
as  regulators  and  candles  only  were  used,  the  imperfect  means 
described  above  were  sufficient.  But  with  incandescent  lamps, 
illuminators  of  very  reduced  intensity,  the  number  of  pieces 
of  apparatus  on  the  same  generator  must  be  considerably  in- 
creased ;  the  problem  of  distribution  then  presented  itself, 
and  it  had  to  be  met  and  solved  more  or  less  completely. 

As  long  as  only  light  was  under  consideration,  the  appa- 
ratus all  being  equal,  their  consumption  of  electricity  could 
be  known  in  advance,  and  the  question  was  accordingly  sim- 
plified. Thus,  the  Electrical  Exposition  of  Paris  contained  a 
certain  number  of  distributions  of  light.  But,  to  tell  the 
truth,  none  were  seen  actually  at  work  ;  the  lights  of  the  Ex- 
hibition were  regulated  once  for  all ;  when  they  were  in  ac- 
tion they  never  changed,  and  the  current-regulators  had  no 
occasion  for  working.  No  special  experiments  seem  to  have 
been  made  to  determine  their  efficiency ;  nevertheless,  they 
are  interesting  to  understand.  We  have  described  already, 
in  Book  IY,  the  current-regulator  of  Maxim  and  Edison.* 
We  add  to  them  that  of  Mr.  Lane-Fox. 

The  regulator  of  current  intensity  of  Mr.  Lane-Fox,  shown 
in  Fig.  201,  has  as  principal  organ  a  sort  of  vibrator  actuated 
by  an  electro-magnet,  E,  and  designed  to  turn  a  ratchet-wheel, 
N,  whose  axis  carries  a  toothed  pinion  placed  between  two 
beveled  wheels,  R  R/,  mounted  on  a  common  axle.  This  axle 
carries  at  its  extremity  a  friction-lever,  F,  which  moves  in 
front  of  a  series  of  contact -pieces,  C  C,  corresponding  to  regu- 
larly increasing  resistances.  According  as  one  or  the  other  of 
the  wheels,  R  R',  moves  the  axle,  and  consequently  the  lever 
in  one  or  the  other  direction,  it  reduces  or  increases  the 
resistances  introduced  into  the  circuit. 

The  axle  of  the  wheels,  R,  R',  can  be  moved  longitudinally 

*  [It  was  found  necessary  to  substitute  for  the  author's  account  a  more  com- 
plete one,  and  to  place  it  after  the  description  of  Marcel  Deprez's  system,  as  the 
reasons  for  its  adoption  could  then  be  better  appreciated.] 


CONDITIONS   OF   A  GENERAL  DISTRIBUTION. 


327 


Tinder  the  influence  of  the  armature  A,  common  to  the  two 
electro-magnets,  E,  E'.  A  relay  with  double-contact,  E",  I, 
placed  in  a  derived  circuit,  sends  into  one  or  the  other  of 
these  electro-magnets  a  local  current ;  the  armature  A  at- 
tracted to  the  right  or  left  moves  the  axle  so  as  to  make  the 
pinion  engage  sometimes  with  one,  sometimes  with  the  other, 
of  the  two  wheels  R,  R/. 

It  remains  to  examine  briefly  the  extent  to  which  these 

apparatus  fulfill  the  conditions  recited  above. 

Edison's  method  consists  in  the  use,  for  exciting 

the  generating  machine,  of  a  derivation  of  the  prin- 


FIG.  201. — Lane-Fox's  regulator  of  current  intensity. 

cipal  circuit.  In  this  derivation  resistances  are  introduced  by 
hand,  according  to  the  indications  of  a  galvanometer,  or  more 
simply  of  a  test-burner.  What  is  lacking  in  this  process  is 
perfectly  clear — it  is  not  automatic,  and  only  suffices  for  a 
preliminary  regulation,  or  for  slight  and  foreseen  variations. 
It  can  not  answer  for  the  service  of  an  extended  and  varied 
distribution  in  which  sudden  and  considerable  changes  occur ; 


328 


DISTRIBUTION   OF  ELECTRICITY. 


accidents  would  happen  before  the  attendant  could  prevent 
them,  admitting  even  that  by  sustained  continuous  attention 
he  may  be  always  ready  to  act.  It  is  a  practically  useful 
method,  sufficing  perhaps  for  most  systems  of  lighting ;  but 
is  not  really  a  general  solution  of  the  problem  of  the  distri- 
bution of  light,  nor,  for  a  stronger  reason,  of  the  distribution 
of  electricity  for  all  the  various  uses  to  which  it  is  adapted. 

The  methods  suggested  by  Messrs.  Lane-Fox  and  Hiram 
Maxim  are  theoretically  more  complete  ;  it  is  not  certain  that 
they  are  more  efficacious.  The  regulators  which  they  employ 
are  very  slow  in  action ;  that  of  Maxim  has  also  the  defect 
of  working  by  the  displacement  of  rubbing  brushes,  which 


FIG.  202. — Diagram  of  Edison  street-mains. 

places  the  machine  always  under  bad  conditions  of  working. 
They  have  only  been  tried  for  the  smaller  class  of  distribu- 
tions ;  it  does  not  appear  that  they  can,  on  account  of  their 
slowness  of  action,  suffice  for  a  really  complicated  and  very 
variable  distribution. 

They  are,  however,  useful  apparatus,  and  give  a  certain 
guarantee  of  security  and  good  working  for  those  apparatus 
to  which  they  have  been  applied.  It  is  true  that  incandescent 
lamps  are  not  very  difficult  apparatus  to  employ  in  division  ; 
they  can  support  considerable  variations  in  intensity  of  cur- 
rent, so  that  the  regulation  is  less  necessary  with  them  than 
with  large  burners,  such  as  regulators  or  candles. 


CONDITIONS   OF  A  GENERAL  DISTRIBUTION. 


329 


II.  ELECTRIC  CANALIZATION  OF  EDISON. 

The  Exhibition  has  shown  us  examples  of  notable  division. 
The  last  plant  of  Mr.  Edison  supported  about  six  hundred 
lamps,  all  placed  on 
his  large  machine.  It 
is  necessary  to  re- 
peat that  this  system 
was  put  in  order  once 
for  all,  and  needed 
no  regulating  while 
working.  His  lamps 
were  placed  in  groups 
of  two  in  derivation, 
on  a  general  circuit. 

Mr.  Edison  has  al- 
so arranged  elsewhere 

much  more  extensive     ^1  Bill  ,lf 

distributions  of  light, 
all  of  whose  accessory 


I 


arrangements  he  has 
studied  out  with  re- 
markable care.  At  the 
Paris  Exhibition  of 
Electricity,  plans  in 
great  detail  were  ex- 
hibited of  the  electric 
canalization  which  at 
this  time  [1882]  is  be- 
ing completed  in  the 
First  District  of  New 

York,  and  which  is  to  supply  fifteen  thousand  lamps  in  sepa- 
rate houses  and  in  public  places. 

[In  this  installation  the  street-mains  consist  of  small 
wrought-iron  pipes,  containing  two  half-round  copper  rods — 
the  outgoing  and  return  conductors — imbedded  in  a  resinous 


330 


DISTRIBUTION   OF  ELECTRICITY. 


insulator.  These  mains  are  laid  underground,  about  two  feet 
below  the  surface,  and  are  arranged  so  that  they  form  a  net- 
work throughout  the  entire  district,  constituting,  in  fact,  a 
gigantic  sieve,  of  which  the  blocks  are  the  meshes.  In  actual 
laying,  a  main  is  carried  around  each  city  block,  and  these 
are  joined  together  at  the  corners  by  means  of  junction-boxes. 
The  arrangement  is  shown  in  Fig.  202,  where  A  represents  the 
city  blocks,  the  full  lines  encircling  them  the  conductors,  and 
B  the  junction-boxes.  These  conductors  are  of  successively 
smaller  diameter  as  they  are  removed  from  the  central  sta- 


FIG.  204. — Edison  junction- box,  with  safety-catch,  for  connection  of  service-wires  with 


tion.  Auxiliary  mains,  termed  feeders,  shown  in  the  dotted 
lines,  serve  to  increase  the  conducting  capacity  to  any  desired 
extent  throughout  any  portion  of  the  system.  The  manner 
in  which  the  dynamos  are  connected  with  the  mains  is  shown 
at  G,  and  the  way  in  which  the  lamps  are  placed  on  the  circuit 
at  L.  The  main  junction-boxes  are  constructed  as  shown  in 
Fig.  203,  in  which  provision  is  made,  by  means  of  the  curved 
metal  arms,  for  expansion  and  contraction.  Similar,  though 
smaller,  boxes  serve  for  the  connection  of  the  service  or  house 
conductors  with  the  mains.  The  construction  of  these  is 
shown  in  Fig.  204.] 


CONDITIONS  OF  A  GENERAL  DISTRIBUTION.  331 

In  these  two  boxes  there  will  be  obseBved  a  wire  interposed 
in  the  branch  circuit ;  it  is  a  safety-catch  of  fusible  metal,  de- 
signed to  cut  off  the  current  if,  by  accident,  it  should  be- 
come strong  enough  to  injure  the  lamps,  or  to  cause  in  the 
conducting  wires  a  dangerous  heat- 
ing. These  boxes  also  enable  the 
circuit,  in  case  of  accident,  to  be 
interrupted  at  the  necessary  point, 
so  as  to  isolate  parts  of  the  circuit 
that  may  be  inaccessible,  while  the 
remainder  is  still  supplied. 

As  for  the  interior  conductors 
for  houses,  these  are  copper  wires,      F'°blf %%£*££ 

Of  proper   Size,  wrapped   in  a  Casing  where  the  wires  enter  a  house. 

of  cotton  rendered   incombustible, 

and,  if  desirable,  finally  covered  with  silk.  The  placing  of 
these  wires  does  not  differ  from  that  already  effected  every- 
where for  electric  bells. 

In  the  path  of  these  conducting  wires  Mr.  Edison  also 
places  little  safety-plates  (Fig.  205). 

Thanks  to  these  multiplied  precautions,  a  fire  is  not  possi- 
ble in  case  of  irregularity  in  the  strength  of  the  current,  from 
heating  the  conducting  wires.  The  cut-off  would,  in  fact,  melt 
long  before  this  heating  would  be  sufficient  to  set  on  fire  the 
most  combustible  materials,  and  would  thus  cut  off  all  pas- 
sage of  a  dangerous  current.  If  electrical  systems  of  other 
kinds  have  sometimes  occasioned  slight  fires,  it  is  precisely 
because  they  have  neglected  those  multiplied  precautions 
which  are  one  of  the  characteristics  of  Edison's  canalization. 

The  lamps  are,  moreover,  as  we  know,  provided  with 
safety-pieces — either  one  for  a  group  or  one  for  each  lamp — 
(Figs.  206,  207),  and  there  is  also  one  in  the  socket  of  each 
lamp,  to  arrest  the  current  at  the  least  irregularity  in  its  be- 
havior. Thus,  no  provision  appears  to  have  been  neglected 
to  reassure  the  most  timid  people. 

The  plants  set  up  in  the  Paris  Exhibition,  of  far  vaster 
proportions  than  any  preceding  ones,  have  succeeded  in  prov- 
ing that  the  division  of  electricity,  like  all  other  divisions, 
was  not  effected  without  loss,  especially  of  light.  As  the 
burners  became  smaller,  the  quantity  of  light  obtained  by  the 
expenditure  of  a  horse-power  in  working  the  machine  became 
less.  The  following  figures  may  be  accepted  as  at  least  proba- 


332 


DISTRIBUTION    OF   ELECTRICITY. 


FIG.  206. — Lamp-socket  with  safety-catch. 


ble  :  with  a  single-arc  regulator  on  a  machine,  an  average  per 
horse-power  was  obtained  of  the  value  of  100  carcels.  M. 
Fontaine  estimates  that  with  Gramme  machines  this  value 

may  rise  to  as  much 
as  280  carcels.  With 
divided-current  lamps 
—differential  lamps, 
for  instance — 80  to  85 
carcels  are  obtained  for 
the  same  expenditure 
of  work.  The  Jabloch- 
koff  candles,  and  the 
Reynier-Werdermann 
incandescent  lamps, 
give  30  to  50  carcels. 
Finally,  the  small  in- 
candescent lamps  with- 
out combustion — of  the  Edison,  Swan,  Maxim,  and  other  sys- 
tems— give  hardly  more  than  10  to  16  carcels  per  horse-power 
expended,  varying  with  the  system  of  lamps  used. 

It  is  clear  that  at  this  point  the  division  becomes  expen- 
sive ;  but  it  then  furnishes  luminous  centers  analogous  to  our 
oil-lamps,  which  cost  us  much  more  than  gas,  and  can  even 
take  the  place  of  candles  that  are  still  more  expensive. 
Neither  must  we  forget  that  lighting  is  not-  the  only  field 
for  the  application 
of  distributed  elec- 
tricity. It  is,  on 
the  contrary,  only 
a  particular  case  of 
a  vast  collection  of 
services  to  which 
electricity  is  admi- 
rably adapted,  and 
which  make  the 
method  of  its  gener- 
al distribution  one 
of  the  most  impor- 
tant problems  im- 
aginable. 

It  is,  in  fact,  an  excellent  means  for  the  transmission  and 
distribution  of  motive  power  ;  it  enjoys  the  valuable  property 


FIG.  207.— View  from  below  of  the  lamp-base. 


CONDITIONS  OF  A   GENERAL  DISTRIBUTION.  333 

of  furnishing  economically  mechanical  power  in  very  small 
fractions,  something  which  no  motor  now  known  to  us  can 
effect.  From  this  point  of  view  alone,  a  general  distribution 
of  electricity  would  be  an  immense  advantage ;  its  value  ap- 
pears still  greater  if  we  consider  the  multitude  of  different 
purposes  to  which  electricity  is  so  readily  applicable,  and 
which  the  Exhibition  of  1881  showed  with  so  much  eclat. 

This  general  problem  does  not  differ  on  the  whole  from 
the  narrower  problem  of  the  distribution  of  the  light  alone  ; 
the  conditions  to  be  fulfilled  are  the  same.  All  that  must  be 
borne  in  mind  is,  that  the  apparatus  to  be  supplied  are  very 
variable,  very  unequal ;  that  the  distances  to  be  overcome  will 
be  greater,  and  the  variations  in  service  more  considerable ;  so 
that  for  success  to  be  attained  all  accessory  conditions  must 
be  fulfilled  with  the  greatest  rigor,  all  approximate  solutions, 
acceptable  in  minor  proportions,  inevitably  failing  as  they  are 
extended  over  wide  areas. 

This  and  other  reasons,  already  given  above,  show  that 
special  methods,  used  for  light,  and  which  we  have  just  de- 
scribed, will  be  entirely  insufficient  for  a  general  distribution 
of  electricity.  For  the  rest,  it  must  be  said  that  their  invent- 
ors never  pretended  to  give  them  this  destination. 

At  the  Electrical  Exhibition  at  Paris  only  two  distribu- 
tions striving  for  the  full  solution  of  the  problem  were  to  be 
seen  :  that  of  M.  Gravier,  and  that  of  M.  Marcel  Deprez.  We 
shall  first  study  that  of  M.  Gravier,  which  is  far  less  complete 
than  the  other. 

III.  M.  GRAVIER' s  SYSTEM  OF  ELECTRICAL  DISTRIBUTION. 

We  have  said,  it  will  be  remembered,  that  the  problem  of 
distribution  would  disappear  if  the  generator  had  no  resist- 
ance. M.  Gravier  at  once  aims  at  this  state  of  affairs  in  re- 
ducing the  resistance  of  the  generator.  For  this  end  he  takes 
several  machines  and  couples  the  armatures  in  quantity, 
which  diminishes  the  resistance  of  the  combined  arrangement ; 
he  connects  the  field  magnets  in  series,  and  produces  their  ex- 
citation either  by  a  derived  circuit  or  by  a  special  machine. 
He  uses  an  outgoing  conductor  that,  according  to  him,  acts  as 
a  reservoir.  It  is  hard  to  understand  what  he  means  by  this, 
as  a  conductor  is  not,  and  can  not  be,  a  reservoir.  All  that 
appears  is  that  he  makes  it  very  large,  which  amounts  to  di- 


334:  DISTRIBUTION   OF  ELECTRICITY. 

ininisMng  its  resistance.  Afterward  lie  divides  it  into  a  cer- 
tain number  of  circuits  going  to  the  separate  pieces  of  appa- 
ratus. 

The  distribution  of  which  we  give  here  the  plan  (Fig.  208) 
is  not  that  of  the  Paris  Exhibition  ;  it  is  a  plant  of  the  same 


FIG.  208. — M.  Gravier's  system  of  electrical  distribution  at  the  Zawiercie  works,  Poland. 

kind  established  in  Zawiercie,  in  Poland ;  it  gives  an  exact 
idea  of  the  method.    . 

It  is  perfectly  clear  that  this  system  does  not  solve  the 
problem  of  distribution  ;  it  does  not  even  attack  it.  It  is  con- 
tent, a  restricted  installation  being  given,  to  indicate  the  con- 
ditions most  favorable  to  a  good  result,  and  that  by  the  appli- 
cation of  a  well-known  physical  principle ;  there  is  nothing 


CONDITIONS  OF  A  GENERAL  DISTRIBUTION.  335 

in  it  constituting  a  special  method.  It  is  easy  to  see  its  de- 
fects. First,  it  does  not  satisfy  any  of  the  three  conditions 
specified  above.  Finally,  it  requires  the  use  of  a  very  con- 
siderable amount  of  material,  for,  to  diminish  the  resistance, 
numerous  machines  must  be  employed  instead  of  a  single 
powerful  generator.  At  Zawiercie,  M.  Gravier  has  four  ma- 
chines for  eight  lamps  ;  at  the  Exhibition  he  had  six  of  them 
for  six  circuits :  such  being  the  conditions,  he  might  as  well 
not  have  divided  his  current  at  all.  Finally,  it  would  be  im- 
possible with  this  system  to  obtain  any  extended  capacity  or 
range ;  the  transmission  of  electricity  can  only  be  accom- 
plished by  giving  the  current  a  quite  high  tension,  and  this  is 
inseparable  from  a  certain  resistance  in  the  generators. 

M.  Gravier  has  invented  a  very  ingenious  regulator  (Fig. 
209)  which  he  calls  either  emission  regulator  or  consummation 
regulator  (regulateur  d/emissions,  regulateur  de  consomma- 
tion\  and  which  serves  to  introduce  suitable  resistances  into 
the  circuits  or  to  withdraw  them.  We  have  seen  how  costly 
this  method  of  regulating  was. 

Finally,  to  complete  his  system  of  regulation,  M.  Gravier 
has  proposed  to  adjust  to  the  lamps  a  small  apparatus  which 
he  calls  a  rheometric  regulator,  and  which  is  shown  in  Fig. 
210.  It  has  for  its  object  the  rendering,  by  the  intervention 
of  the  derived  current,  the  regulation  of  the  machine  more 
rapid,  an  intervention  which  is  not  ordinarily  produced  except 
when  this  derivation  acquires  a  power  sensibly  greater  than 
that  which  balances  the  magnetic  action. 

This  regulator  is  composed  of  a  two-armed  electro-magnet 
(Fig.  210)  placed  in  derivation,  but  whose  circuit  is  opened 
or  closed  instantaneously  by  the  needle  of  a  fine  wire  galva- 
nometer of  M.  Marcel  Deprez,  a  galvanometer  which  is  itself 
placed  on  another  shunt  from  the  principal  circuit.  The 
action  of  the  electro-magnet  on  the  releasing  armature,  shown 
opposite  the  left-hand  arm,  is  thus  more  complete  and  more 
prompt ;  the  movement  of  the  galvanometer-needle  which  de- 
termines the  opening  and  closing  of  the  circuit,  and  conse- 
quently the  motion  or  stoppage  of  the  mechanism,  is  effected 
by  a  variation  in  distance  scarcely  exceeding  a  tenth  of  a  mil- 
limetre ;  the  regulation  thus  becomes  much  more  exact  and 
more  rapid.  This  arrangement  was  applied  to  the  lamps 
which  M.  Gravier  had  working  at  the  Electrical  Exhibition  at 

Paris. 

•23 


336 


DISTRIBUTION  OP  ELECTRICITY. 


FIG.  209.— M.  Gravicr's  Ecgulator. 

TJ,  electric  generator,  single  or  multiple,  according  to  the  works. 

E,  net- work  of  conductors. 

v,  point  of  distribution  recognized  as  that  most  liable  to  be  short  of  electricity ;  from  this 

point  the  net-work  communicates  with  the  works  by  a  special  wire,  which  M.  Gravier 

calls  his  return  wire ;  and  upon  which  is  placed  a  fine  wire  galvanometer  of  M.  Desprez, 

to  indicate  all  the  variations  produced  at  the  point  v. 
A  B,  horseshoe  electro-magnet,  whose  wire  is  wound  around  the  middle  portion,  and  whose 

arms  A  and  B  arc  the  expansions  of  the  two  poles. 


CONDITIONS   OF  A  GENERAL  DISTRIBUTION. 


337 


5,  i,  vibrating  armature  of  the  electro-magnet  A,  B.  It  carries  on  each  side  springs,  c,  c% 
arranged  to  come  in  contact  with  other  springs,  £,  £,  and  to  determine  the  passage  of  a 
local  current,  cither  in  one  or  the  other  direction,  through  the  bobbins  B  s.  The  springs 
are  insulated  at  *,  *,  i. 

P,  counterpoise  serving  to  oppose  the  action  of  the  electro-magnet  on  its  armature. 

B  5,  rotating  armature  (Siemens  or  other),  turning  from  left  to  right,  or  from  right  to  left, 
according  to  the  direction  of  the  local  current  traversing  the  magnet. 

/•>/•>  positive  and  negative  brushes  for  entrance  and  departure  of  the  local  current  in  the 
bobbin,  B  s. 

The  variations  of  the  return  current  cause  the  energy  of  the  electro-magnet,  A,  B,  to 
increase  or  diminish,  and  consequently  the  armature  will  touch  the  contact-pieces,  some- 
times at  c,  sometimes  at  c',  thus  determining  the  passage  of  the  local  current  in  the  bob- 
bin. As  long  as  the  return  current  preserves  the  normal  state  for  which  its  regulating 
mechanism  has  been  adjusted,  the  armature  remains  in  equilibrium,  and  the  bobbin  B  s 
remains  motionless ;  but  if  the  return  current  changes  in  intensity,  the  strength  of  the 
electro-magnet,  A,  B,  will  be  increased  or  diminished ;  the  armature  will  yield  either  to 
the  preponderating  action  of  the  weight  P,  or  to  the  attraction  of  the  electro-magnet ;  it 
will  close  one  of  the  contacts  c  or  c',  and  will  determine  the  passage  of  the  local  current 
into  the  movable  armature,  which  begins  to  turn  in  one  or  the  other  direction  5  it  is  this 
rotation  which  M.  Gravier  utilizes  for  making  his  electro-motive  force  vary,  either  by 
modifying  the  speed  of  the  motor  or  by  introducing  resistances  in  the  excitation  circuit. 


FIG.  210.— Rheometric  regulator  of  M.  Gravier. 


The  apparatus  of  M.  Gravier  have  not  yet  been  placed  in 
practical  working,  and  in  questions  of  this  sort,  from  our 
present  point  of  view,  those  systems  are,  above  all,  worthy 
of  confidence  which  have  received  the  decisive  test  of  experi- 
ence. This  guarantee  is  not  wanting  to  the  last  solution  which 
we  have  to  examine,  the  important  discovery  of  M.  Marcel 
Deprez. 


338  DISTRIBUTION   OF  ELECTRICITY. 

IV.    SYSTEM  OF  ELECTRICAL  DISTRIBUTION  OF  M.  MARCEL 

DEPREZ. 

By  a  special  study  of  the  working  of  machines,  M.  Deprez 
found  that  the  regulation  necessary  for  distribution  could  be 
obtained  from  the  machines  themselves,  using  only  their  own 
proper  action  suitably  combined,  and  without  the  intervention 
of  mechanical  organs. 

To  understand  the  system,  it  must  first  be  remembered 
that  the  work  produced  by  a  steam-engine  does  not  depend 
upon  its  speed,  but  on  the  quantity  of  steam  which  it  expends 
and  on  the  pressure.  In  large  factories,  where  a  central  engine 
drives  numbers  of  machines,  its  rate  of  speed  does  not  change, 
whatever  be  the  number  of  machines  that  are  working ;  but  it 
only  admits  each  moment  the  quantity  of  steam  that  is  neces- 
sary for  it,  thus  regulating  its  work  by  the  demand.  It  is 
the  same  with  a  gas-engine,  which  only  admits  gas  in  propor- 
tion to  its  needs,  always  preserving  the  same  speed. 

In  like  manner,  dynamo-electric  machines  can  expend 
more  or  less  power  without  change  of  speed ;  it  depends  on 
the  magnetization  of  their  field  magnets— a  magnetization 
which  determines  the  eifort  necessary  to  put  them  in  motion  ; 
it  is  enough,  in  fact,  to  modify  this  magnetization,  to  cause  to 
vary  at  the  same  time  the  work  produced  and  work  expended 
by  a  machine. 

M.  Marcel  Deprez  determines  once  for  all  the  speed  of  his 
electric  machine  and  of  his  engine :  he  varies  the  work  by 
varying  the  magnetization. 

When  the  apparatus  to  be  supplied  is  placed  in  deriva- 
tion, a  single  condition  suffices  to  insure  their  independence  ; 
it  is  necessary  that  the  electrical  state  at  the  two  ends  of  the 
machine  be  always  the  same,  whatever  the  exterior  circuit. 
It  is  evident  then,  that  if  the  machine  be  regulated  so  as  to 
fulfill  this  condition,  each  circuit  will  be  practically  separate, 
and  consequently  have  perfect  independence. 

Under  the  ordinary  conditions  of  dynamo-electric  ma- 
chines, the  electric  state  of  the  terminals  of  the  machine,  what 
is  called  the  difference  of  potential  of  these  points,  is  deter- 
mined, for  a  given  speed,  by  the  excitation  of  the  field  ;  this 
is  produced  by  the  current  of  the  machine  itself,  and  conse- 
quently varies  with  the  conditions  of  the  circuit.  The  differ- 
ence of  potential  varies  at  the  same  time.  To  keep  constant 


34:0 


DISTRIBUTION   OF  ELECTRICITY. 


this  difference  of  potential,  M.  Marcel  Deprez  obtains  the  ex- 
citation of  the  field  from  two  distinct  currents,  whose  effects 
are  added  to  each  other ;  one  of  them  is  a  constant  current 
furnished  by  an  independent  source  of  electricity,  either  a 
battery  or  a  second  machine.  The  other  is  the  current  pro- 
duced by  the  machine  itself,  and  utilized  in  the  exterior  cir- 
cuit. These  two  currents  traverse  two  distinct  sets  of  coils, 
formed  of  wires  wound  side  by  side,  so  that  adjacent  wires  are 
sensibly  at  the  same  distance  from  the  magnetized  core.  The 
speed  of  the  machine  is  regulated  to  a  fixed  value  resulting 
from  its  construction. 

With  this  construction,  there  will  always  be  two  electro- 
motive forces  in  the  machine ;  one  invariable,  produced  by 
the  special  exciting  current,  and  which  corresponds  to  the  in- 
terior resistance,  also  invariable,  of  the  machine ;  the  other, 

which  is  produced  by  the 
working  current,  and  which 
increases  or  diminishes  in  in- 
verse ratio  to  the  resistance 
of  the  exterior  circuit.  It 
follows  that,  without  chang- 
ing the  speed  of  the  machine, 
the  difference  of  potential 
produced  by  the  exterior  ex- 
citation is  kept  permanent 
and  invariable.  The  machine 


regulates  itself,  without  any 
other  intervention,  and  fur- 
nishes each  instant  the  total 
quantity  of  electricity  neces- 
sary to  the  working  of  the 
different  apparatus. 

It  is  evident  that  on  long 
circuits  and  with  numerous 
derivations  the  difference  of 
potential  will  not  remain  the 
same  over  the  entire  length 
of  the  conductors  ;  this  is 
what  happens  in  all  cases  of 

distribution,  with  water,  gas,  etc.  But  this  presents  no  diffi- 
culty ;  it  is  enough  to  calculate  the  loss  of  the  charge  so  as 
to  know  what  pressure  is  to  be  used  at  each  point  of  the  cir- 


Fio.   212.— Marcel  Deprez  winding  for  con- 
stant electro-motive  force. 


CONDITIONS  OF  A   GENERAL  DISTRIBUTION. 


341 


cuit ;  this  can  be  done  equally  and  with  great  precision  for 
electricity. 

It  is  to  be  remarked  that  this  method,  based  on  rigorous 
mathematical  theorems,  gives  us  the  solution  of  the  question 
of  distribution  in  the  two 
systems — that  is  to  say,  in 
placing  the  apparatus  either 
in  series  or  in  derivation. 
In  practical  working  it  is 
clear  that  the  connections 
of  the  machines  should  be 
modified  according  to  the 
system  adopted,  and,  for 
distribution  in  series,  the 
exciting  of  the  magnets 
should  be  produced  by  a 
derived  current  from  the 
main  circuit.  But  a  sim- 
ple switch  will  suffice  for 
this  change,  and  the  same 
machine  can  serve  alterna- 
tively, without  change  of 
speed,  for  circuits  arranged 
according  to  both  systems. 

[The  methods  of  winding  adopt-       FIG.  213.— Marcel  Deprez  winding  for  constant 
ed  by  M.  Marcel  Deprez  in  these  two  current, 

different  cases  are  shown  very  clear- 
ly in  Figs.  212,  213.  When  the  apparatus  to  be  operated  are  in  multiple  arc— as 
is  always  the  case  with  incandescent  lamps — the  dynamo  is  required  to  give  a 
current  varying  in  compliance  with  varying  demands  of  the  circuit,  but  always 
of  the  same  electro-motive  force.  The  winding  to  accomplish  this  is  shown  in 
Fig.  212.  The  coils  traversed  by  the  constant  current  from  an  external  generator 
are  shown  by  the  dotted  lines,  and  those  traversed  by  the  main  current  produced 
by  the  machine  by  the  full  lines.  The  field  magnets,  it  will  be  seen,  are  placed 
in  the  main  circuit — that  is,  the  winding  is  that  known  as  the  "series  dynamo." 
To  adapt  this  mode  of  regulation  to  apparatus  arranged  in  series  it  is  necessary  to 
place  the  field  in  shunt,  as  shown  in  Fig.  213.  That  these  methods  of  winding 
dynamos  should  accomplish  their  purpose— the  preservation  of  a  constant  elec- 
tro-motive force  in  one  case  and  of  a  constant  current  in  the  other — the  mag- 
netization of  the  field  magnets  must  be  far  from  the  point  of  saturation,  and  the 
machine  must  be  driven  at  a  certain  velocity,  to  be  determined  in  each  case.] 

As  will  be  easily  understood,  this  solution,  reposing  on  the 
play  of  electric  forces,  and  not  on  a  material  organ,  is  abso- 


DISTRIBUTION   OF  ELECTRICITY. 


lutely  general.  It  corresponds  in  the  most  complete  way  to 
the  requisite  conditions ;  it  admits  all  tensions,  and  nothing 
limits  its  applicability ;  finally,  it  has  been  confirmed  by  a 
decisive  experiment  that  lasted  during  the  whole  duration  of 
the  Paris  Exhibition  of  1881. 

The  electric  generator  (Fig.  214)  was  composed  of  a  Gramme 
machine,  taking  a  part  of  its  exciting  current,  according  to 
the  method  already  described,  from  the  constant  current  of 
another  small  machine.  The  speeds  were,  two  thousand  revo- 
lutions for  the  generator,  eight  hundred  for  the  exciter,  and 


FIG.  214. — Arrangement  of  dynamos  for  the  distribution  of  electricity  on  the  system  of  M. 

Marcel  Deprez. 

one  hundred  and  sixty  for  the  gas  engine.  From  the  poles 
of  the  generator  two  cables  issued,  forming  the  principal  cir- 
cuit ;  at  all  useful  points  there  was  taken  from  these  cables, 
by  means  of  two  wires,  a  derived  current,  which  was  conducted 
to  any  given  receptor,  electric  motor,  lamp,  electroplating 
trough,  etc. 

Of  the  two  arrangements  of  the  working  apparatus,  in 
series  or  in  derivation,  this  last  is  the  most  practical,  and 
should  be  preferred  in  the  great  majority  of  cases.  All  the 
systems  we  are  describing  have  adopted  it.  It  requires  a 


CONDITIONS  OF  A  GENERAL  DISTRIBUTION.  343 

less  extensive  regulation,  and  leaves  the  individual  apparatus 
more  independent  of  each  other  ;  it  is  more  reliable  than  the 
arrangement  in  series,  with  which  a  fault  in  a  single  point, 
wherever  it  is,  influences  seriously  all  the  rest  of  the  system. 

We  need  not  add  that  the  distribution  of  M.  Marcel  Deprez 
requires  no  special  construction  of  the  conductors;  it  accommo- 
dates itself  to  all  methods,  and  admits  of  the  employment  of 
all  useful  arrangements  that  practical  experience  may  dictate. 
Following  the  course  of  logic,  M.  Marcel  Deprez  seems  to  have 
desired  to  establish  his  solution  on  solid  bases,  before  devot- 
ing himself  to  accessory  points. 

The  circuit  went  all  around  the  Exhibition  buildings  ;  the 
entire  number  of  apparatus  which  it  kept  in  action  varied  from 
twenty  to  twenty-seven ;  these  apparatus,  on  the  other  hand, 
worked  with  complete  independence;  they  were  far  apart, 
and  the  workmen  in  charge  of  their  operation  worked  without 
regard  to  what  was  going  on  in  other  parts  of  the  system.  In 
the  circuit  there  were  placed  machines  for  making  metallic 
braid,  sewing-machines,  saws,  metal  working-lathes,  voltaic- 
arc  lamps,  incandescent  lamps ;  in  private  exhibitions,  venti- 
lators, electroplating  troughs,  the  "  melographe  repetiteur" 
of  M.  Carpentier.  Finally,  at  the  end  there  was  placed  a  Ma- 
rinari  printing-press,  on  which  were  printed  the  numbers  of 
the  journal  "La  Lumiere  Blectrique,"  and  various  circulars. 
For  the  smaller  class  of  apparatus  the  motor  employed  was 
the  small  magneto-electric  motor  of  Marcel  Deprez ;  for  the 
printing-press  it  was  a  small  Siemens  machine.  All  this  col- 
lection moved  with  perfect  regularity  and  an  absolute  inde- 
pendence. As  all  can  testify,  the  gas-engine  driving  the  elec- 
tric generator  showed,  by  the  variation  in  its  consumption  of 
gas,  that  the  work  expended  was  in  exact  proportion  to  the 
work  utilized  throughout  the  extent  of  the  circuit.  The  ex- 
periment thus  combined  all  necessary  conditions,  and  should 
be  considered  absolutely  conclusive.  Furthermore,  the  con- 
siderations upon  which  M.  Marcel  Deprez  bases  his  system 
are  so  clear  and  rigorous  that  its  first  success  never  seemed 
doubtful.  It  will  be  the  same  with  experiments  on  the  large 
scale,  which  will  soon  be  tried,  and  which  will  complete  the 
practical  demonstration  of  the  system. 

From  now  on,  this  elegant  solution  of  a  problem  as  difficult 
as  important  can  be  considered  as  achieved.  It  is  complete 
in  other  ways,  because,  independently  of  his  studies  on  dis- 


DISTRIBUTION  OF  ELECTRICITY. 


tribution,  M.  Deprez  lias  completed  experiments  on  the  trans- 
mission of  power  by  electricity,  which  have  elucidated  this 
question,  still  somewhat  obscure,  and  have  shown  its  true  con- 
ditions. It  will  not  be  impossible,  then,  soon  to  try  the  utili- 
zation of  natural  .forces  hitherto  lost,  such  as  waterfalls  that 
are  inaccessible  or  too  remote  from  working  centers.  Then 
the  extreme  division  of  light,  so  costly  under  other  conditions, 
will  become  economically  possible,  the  power  employed  being 
of  low  cost.  But  this  would  only  be  an  insignificant  part  of 
the  advantages  that  would  be  obtained,  and  every  one  can  see 
the  measure  of  consequences  indicated  by  the  expression 
"  electricity  in  the  home  " :  it  is  at  once  light,  power,  chemical 
work,  placed  within  the  reach  of  every  one,  in  as  small  frac- 
tions as  can  be  wished  for,  with  no  trouble  beyond  turning 

a  key.  From  this  time  the 
fact  can  be  considered  ac- 
complished, and  we  can 
await  with  confidence  the 
vast  and  impending  devel- 
opment. 

[A  method  of  making 
a  dynamo  self  -  regulating, 
analogous  to  that  of  M. 
Deprez,  has  been  devised 
by  Professor  John  Perry. 
As  the  purpose  of  the  cur- 
rent from  an  external  source 
in  the  Deprez  arrangement 
is  simply  to  maintain  an  in- 
itial and  independent  mag- 
netic field,  any  other  means 
that  will  accomplish  this 
can  be  employed.  In  Pro- 
fessor Perry's  machine  for 
maintaining  a  constant  elec- 
tro-motive force,  shown  in 
Fig.  215,  a  separate  mag- 
neto machine  is  included 
in  the  circuit  of  a  series  dynamo,  and  is  driven  at  such  a  speed 
as  will  maintain  the  desired  electro-motive  force  between  the 
terminals  of  the  dynamo.  In  the  machine  for  constant  cur- 
rent, the  magneto  is  placed  in  the  shunt  circuit  (Fig.  216)]. 


FIG.  215.— Professor  Perry's  machine  for  con- 
stant electro-motive  force. 


CONDITIONS   OF  A  GENERAL  DISTRIBUTION. 


345 


Y.  EDISON'S  METHOD  OF  REGULATION. 

[The  Deprez  method  of  regulation  for  machines  with  con- 
stant electro-motive  force  was  devised  by  Mr.  Edison  some 
time  previous  to  any  public  exhibition  by  M.  Deprez,  and  was 
patented  in  this  country 
in  September,  1882.  The 
illustration  (Fig.  217)  is  a 
reproduction  of  the  draw- 
ing from  this  patent.  The 
circuit  3,  4,  serving  to  main- 
tain an  initial  magnetism 
in  the  field,  is  here  shown 
as  a  shunt  to  the  main  cir- 
cuit, but  Mr.  Edison  states 
in  his  specification  that  the 
current  through  it  may  be 
supplied  from  an  external 
source.  When  this  circuit 
is  a  shunt,  it  is  made  of 
high  resistance,  so  that  the 
amount  of  current  flowing 
through  it  will  not  vary 
much  within  the  limits  of 
probable  variation  of  resist- 
ance in  the  main  circuit. 
As  previously  stated,  in 
order  that  this  method  of 
regulation  should  work  sat- 
isfactorily, the  dynamo  must  be  driven  at  a  constant  velocity. 
The  maintaining  of  a  constant  velocity  is,  however,  much 
more  difficult  than  would  be  imagined.  Mr.  Edison  was,  in 
fact,  compelled  to  abandon  this  construction  on  this  account, 
as  he  found  that  the  variation  in  the  speed  of  his  driving- 
engine  produced  greater  variations  in  his  circuit  than  that 
due  to  the  turning  on  and  off  of  the  lamps  under  normal  con- 
ditions of  lighting. 

He  has  therefore  adopted  a  mode  of  regulation  which  will 
enable  the  variation  from  both  of  these  causes  to  be  met. 
The  method  consists  in  interposing  in  the  shunt  circuit,  in 
which  the  field  magnets  are  placed,  an  adjustable  resistance. 
When  the  number  of  lamps  in  circuit  is  increased,  resistance 


FIG.  216. — Professor  Perry's  machine  for  con- 
stant current. 


JO,       C 


2  1 

FIG.  217. — Edison  dynamo  with  compound  winding,  for  constant  electro-motive  force. 


CONDITIONS   OF  A   GENERAL  DISTRIBUTION.  347 

is  thrown  out  of  the  field  circuit,  and,  when  they  are  dimin- 
ished, it  is  introduced.  Similarly,  when  the  speed  increases, 
resistance  is  thrown  into  the  field  circuit,  and  taken  out  when 
this  diminishes.  The  electro-motive  force  of  the  current  can 
thus  be  kept  practically  constant,  whatever  the  changes  in  the 
working  circuit.  At  central  stations  the  shifting  of  these  re- 
sistances is  done  by  hand,  but  their  manipulation  is  effected 
automatically  in  separate  plants  of  moderate  size,  such  as 
those  designed  for  lighting  workshops,  large  buildings,  etc. 
The  difficulties  in  the  way  of  an  automatic  regulation  of  very 
large  plants,  such  as  those  operated  from  a  central  station,  are 
considerable,  and  Mr.  Edison  has  always  preferred  to  have  a 
mode  of  regulation  as  free  as  possible  from  mishaps.  The 
Deprez  method  of  regulation  he  only  intended  to  use  with 
isolated  plants. 

The  regulation,  as  carried  out  at  the  central  station  of  the 
first  district  in  New  York  city,  consists  in  varying  the  field 
resistance  in  accordance  with  the  indications  of  a  galva- 
nometer placed  in  a  Wheatstone  bridge.  An  incandescent 
lamp  is  placed  on  one  side  of  the  bridge,  and  the  variable 
resistance  of  the  bridge  adjusted  so  that  the  galvanometer- 
needle  stands  at  zero  when  the  lamp  is  giving  its  normal  light. 
As  the  resistance  of  the  incandescent  carbon  filament  varies 
with  its  temperature,  any  change  in  the  current  flowing 
through  the  lamp  will  immediately  destroy  the  balance  of  the 
bridge  and  cause  the  needle  to  move  in  one  direction  or  the 
other,  according  as  the  lamp  rises  or  falls  in  candle-power. 
Resistance  is  then  introduced  into  or  thrown  out  of  the  field 
circuit  until  the  needle  returns  to  its  normal  position.  These 
resistances,  which  consist  of  coils  of  German-silver  wire,  can 
be  readily  manipulated  by  the  attendant  by  means  of  a  switch. 
It  might  be  supposed  that  this  duty  would  require  constant 
watchfulness  on  the  part  of  the  attendant,  but  this  is  far 
from  being  the  case.  In  any  extensive  distribution  the  vari- 
ation in  the  demand  for  light  is  a  calculable  one,  and,  the 
greater  the  number  of  consumers,  the  more  easily  the  amount 
and  time  of  these  variations  can  be  foreseen.  When  the  sta- 
tion was  first  started  there  was  little  or  no  regularity  in  these 
variations,  as  consumers  were  constantly  turning  lights  on 
and  off  to  show  friends  how  easily  it  could  be  done.  With 
the  attainment  of  normal  conditions,  however,  these  variations 
have  assumed  such  a  regularity  that  Mr.  Edison  asserts  that 


348 


DISTRIBUTION  OF  ELECTRICITY. 


it  is  possible  to  run  the  dynamos  from  a  chart,  in  which  the 
amounts  of  the  resistances  to  be  introduced  into  or  withdrawn 
from  the  field  circuit  are  indicated  by  the  lengths  of  the  ordi- 

nates  of  a  curve,  the  time 
being  denoted  on  the  hori- 
zontal line. 

The  automatic  appara- 
tus and  its  relation  to  the 
machine  are  shown  in  dia- 
gram in  Fig.  218,  and  its 
external  appearance  in  Fig. 
219.  The  resistance  coils 
A,  ^,  which  are  included 
in  the  field  circuit  7,  8, 
are  connected  with  metal- 
lic plates  i,  separated  from 
each  other  by  mica.  The 
upper  edges  of  these  plates 
form  the  arc  of  a  circle, 
along  which  sweeps  the 
elastic  contact  #,  connected 
with  the  arm  D.  The  move- 
ment of  7c  is  produced  by 
the  rocking  -  lever  E,  the 
armatures  I  and  I'  of  which 
are  attracted  by  the  elec- 
tro-magnets C  and  C'. 
Dash-pots  F  and  F'  serve 

to  steady  the  motion  of  the  lever.  The  magnets  C  and  C' 
are  placed  in  the  shunt  circuit  5,  6,  which  is  closed  through 
one  or  the  other  of  them  according  as  the  armature  c  makes 
contact  with  /  or  /'.  This  latter  armature  is  operated  by 
the  electro-magnet  B,  placed  in  another  shunt  circuit  3,  4. 
This  magnet  is  thus  connected  with  the  main  conductors  in 
the  same  way  as  the  lamps  b,  and  will  be  affected  in  the  same 
manner  by  variations  in  the  line-current.  When  lamps  are 
added,  less  current  will  flow  momentarily  through  B,  which 
will  become  weakened  so  as  to  allow  its  armature,  c,  to  be 
drawn  back  by  the  spring  e,  and  make  contact  with  f.  The 
magnet  C'  will  therefore  draw  down  its  armature  Z',  and  move 
7c  along  the  plates  of  the  resistance  coils,  cutting  resistance 
out  of  the  field  circuit.  When  lamps  are  removed,  the  mag- 


FIG.  218. — Diagram  of  the  Edison  automatic  reg- 
ulator. 


350  DISTRIBUTION   OF  ELECTRICITY. 

net  C  will  be  energized  and  resistance  thrown  into  the  field 
circuit.  A  decrease  of  the  speed  of  rotation  of  the  armature 
will  operate  the  same  as  an  addition,  and  an  increase  of  speed 
the  same  as  a  diminution  of  lamps.  To  prevent  the  burning 
out  of  the  contact-points  f  and  /',  the  magnets  C  and  C'  are 
provided  with  shunt-circuits,  9,  for  the  currents  due  to  the 
discharge  of  these  magnets.] 

VI.  WESTON'S  METHOD  OF  REGULATION. — BRUSH  REGU- 
LATOR. 

[Mr.  Weston  has  sought  to  construct  a  machine  of  constant 
electro-motive  force  for  incandescent  lighting,  by  establishing 
a  certain  definite  relation  between  the  field  of  force  and  the 
rotating  armature.  The  nature  of  this  improvement  is  given 
by  Mr.  Weston,  in  his  American  patent,  as  follows  : 

"  My  improvements  consist  in  so  organizing  the  machine 
used  for  supplying  current  in  the  multiple-arc  system  of  dis- 
tribution that,  by  a  law  of  operation  of  the  machine,  the  elec- 
tro-motive force  is  maintained  practically  uniform,  whatever 
may  be  the  quantity  of  current  generated  within  the  practical 
working  limits  of  the  machine.  To  accomplish  this  result  I 
have  found  it  necessary  to  so  construct  the  machine  that  the 
inductive  influence  of  the  field  magnets  in  determining  the 
polarity  of  the  armature-core  shall  so  far  preponderate  over 
that  of  the  induced  currents  circulating  in  and  around  the 
armature  itself,  that  the  effect  of  the  latter  is  neutralized,  at 
least  to  such  an  extent  that  the  polar  line  of  the  armature 
and  that  of  the  field  shall  at  all  times  during  the  normal 
operation  of  the  machine  practically  coincide.  ...  I  also 
wind  the  armature  in  such  manner  that  the  requisite  electro- 
motive force  is  obtained  with  comparatively  few  convolutions 
of  conductors  of  large  cross-section.  It  is  important  to  use 
the  smallest  possible  number  of  convolutions  of  conductor  on 
the  armature,  in  order  to  reduce  to  a  minimum  the  magnetiz- 
ing influence  of  the  armature  coils  upon  the  core,  and  the  re- 
sistance of  the  armature  conductors  is  made  as  low  as  possible 
in  order  that  the  ratio  of  the  external  and  internal  resistances 
may  not  be  greatly  disturbed  by  variations  in  the  external 
circuit.  The  purpose  of  this  will  be  understood  by  a  con- 
sideration of  the  magnetic  condition  of  the  armature-core  of 
a  machine  having  an  ordinary  cylindrical  or  annular  arma- 


CONDITIONS  OF  A  GENERAL  DISTRIBUTION. 


351 


ture,  with  the  coils  wound  in  a  direction  parallel  to  the  axis 
of  rotation.  In  such  case  the  position  of  the  polar  line,  or 
the  points  of  maximum  magnetic  effect  of  the  armature-core 


FIG.  220. — Weston  automatic  regulator  for  arc  lighting. 

during  the  normal  operation  of  the  machine,  is  determined 
partly  by  the  induced  currents  flowing  in  the  armature  coils 


352 


DISTRIBUTION  OF  ELECTRICITY. 


and  circulating  in  the  body  of  the  armature  itself,  both  of 
which  tend  to  fix  the  polar  line  at  right  angles  to  that  of  the 
field,  and  partly  by  the  magnetic  induction  of  the  field,  which 
tends  to  cause  the  polar  line  of  the  armature  to  coincide  with 
its  own.  As  a  result  of  the  combined  effect  of  these  forces, 
the  polar  line  of  the  armature  will  lie  between  the  two  points 
indicated.  This  is  apparent  from  the  fact  that  in  all  machines 
of  this  class,  so  far  as  my  information  extends,  the  maximum 
points  of  the  commutator,  or  the  line  upon  which  the  brushes 
are  placed  to  take  off  the  maximum  amount  of  current,  are 

in  advance  of  the  theoretical  maxi- 
mum points,  which  are  on  a  line  at 
right  angles  to  the  polar  line  of  the 
field,  and  they  are  more  or  less  ad- 
vanced in  proportion  to  the  strength 
of  the  current  induced  in  the  arma- 
ture coils,  and  the  consequent  mag- 
netizing influence  exerted  thereby. 
Probably  the  fluctuations  in  electro- 
motive force  observed  in  such  ma- 
chines are  due  largely  to  this  angular 
displacement  of  the  poles  of  the  arm- 
ature, acting  substantially  in  the  same 
manner  to  reduce  the  lines  of  force 
cut  by  the  coils  as  would  the  removal 
of  the  field  magnets  to  a  greater  dis- 
tance from  the  armature.  I  have 
found  that  if  the  conditions  which  I 
have  indicated  above  are  properly  ob- 
served in  constructing  the  machine, 
the  polar  line  of  the  armature  may  be 
made  to  coincide  with  the  polar  line  of 

the  field,  and  the  real  maximum  points  on  the  commutator  be 
made  to  coincide  so  accurately  with  the  theoretical  points  that 
the  external  resistance  may  be  varied  to  any  extent  within  the 
working  limits  of  the  machine  ;  or  the  machine  may  even  be 
run  in  either  direction  without  changing  the  adjustment  of 
the  brushes,  and  the  electro-motive  force  will  be  practically 
constant  for  a  given  speed  of  rotation  of  the  armature." 

The  Weston  method  of  regulation  for  arc-lamp  circuits  con- 
sists in  introducing  and  withdrawing  resistance  from  the  field 
circuit,  which  is  a  shunt  to  the  main  circuit.  The  apparatus 


FIG.  221.— Details  of  the  Wes- 
ton automatic  regulator. 


CONDITIONS   OF  A  GENERAL  DISTRIBUTION. 


353 


for  doing  this  is  shown  in  Fig.  220,  and  the  details  of  its 
mechanism  in  Fig.  221.  The  resistances  are  cut  in  or  out  of 
circuit  by  the  movement  of  the  arm  J,  which  turns  about  J' 
as  a  center,  its  upper  end  sweeping  over  a  set  of  contacts  ar- 
ranged in  a  circle.  Movement  is  given  to  it  by  the  toothed- 
wheels  R,  R',  which  are  operated  by  the  vibrating  pawls  P,  P', 
and  are  kept  in  motion  by  the  pulley  D.  In  normal  position 
these  pawls  are  clear  of  the  wheels  R,  R7,  but  one  or  the  other 


FIG.  222.— Brush  automatic  regulator. 

of  them  will  be  thrown  into  gear  according  as  the  electro-mag- 
net M,  to  whose  armature  m  the  pawls  are  connected  by  the 
lever  Z,  or  the  opposing  spring  S  is  the  stronger.  This  electro- 
magnet is  placed  in  the  main  circuit,  so  that  it  is  affected  by 
variations  in  the  lighting  current,  the  same  as  the  arc-lamp. 


354:  DISTRIBUTION  OF  ELECTRICITY. 

In  the  Brush  machine  for  arc-lighting  the  field  is  in  series 
with  the  lamps,  and  the  regulation  is  affected  by  placing  re- 
sistance in  and  out  of  a  circuit  forming  a  shunt  across  the 
field  magnets.  A  carbon  rheostat  is  used  instead  of  wire 
coils,  the  resistance  of  which  is  varied  by  pressing  the  plates 
of  which  it  is  composed  more  strongly  together.  This  press- 
ure is  applied  by  means  of  a  lever  operated  by  an  electro- 
magnet, the  coils  of  which  are  in  the  lighting  circuit.  This 
magnet  is  also  provided  with  coils  included  in  the  shunt  cir- 
cuit, in  which  the  rheostat  is  placed,  to  increase  its  sensitive- 
ness. The  construction  is  shown  in  Fig.  222.] 


CHAPTER  III. 

ECONOMY  OF  CONDUCTORS. 

[As  every  electric  conductor  possesses  resistance,  a  portion 
of  the  electric  energy  transmitted  must  always  be  expended 
in  heating  it,  and  therefore  lost  for  any  useful  purpose.  The 
resistance  can,  of  course,  be  made  as  small  as  desired  by 
simply  enlarging  the  conductor,  but  the  limit  in  this  direc- 
tion is  soon  reached,  as  account  has  to  be  taken,  in  practical 
construction,  not  only  of  the  loss  of  power,  but  of  the  cost 
of  the  conductors.  It  is  necessary,  therefore,  to  choose  the 
size  of  conductor  with  reference  to  both  of  these  items,  in 
order  to  obtain  the  maximum  of  economy.  This  condition  is 
realized,  Sir  William  Thomson  has  shown,  when  the  yearly 
interest  on  the  cost  of  the  conductor  equals  the  expense  of 
the  power  lost  in  heating  it. 

How  large  a  portion  of  the  total  power  transmitted,  this 
part  lost  in  heating  the  conductor  is,  will  depend  upon  the 
relation  of  the  two  factors — current- strength  and  electro- 
motive force — which  measure  the  amount  of  electric  energy. 
Since  the  heat  produced  in  a  given  resistance  varies  as  the 
square  of  the  current  flowing  through  it,  it  is  obvious  that,  to 
obtain  the  maximum  economy  in  transmitting  any  given 
amount  of  electric  energy,  we  must  have  a  small  current  and 
high  electro-motive  force.  A  simple  analysis  will  show  the 
relation  between  the  size  and  cost  of  conductor,  and  the 


ECONOMY  OF  CONDUCTORS.  355 

strength  of  current,  with  the  transmission  of  the  same 
amount  of  energy. 

Let  C  =  current  flowing  through  a  circuit  having  a  resist- 
ance, E,  per  unit  of  length.  Then  C2  R  =  loss  by  heating  of 
the  conductor  per  unit  of  length.  In  any  other  conductor  of  a 
resistance  R!  per  unit  of  length,  the  loss  by  heating  in  con- 
veying a  current,  Ci  will  be  C2i  Rt.  Taking  the  loss  the  same 
in  both  cases— that  is,  C2  E  =  d8  RI—  we  have  C2  :  C2!  =  Rx  :  R, 

/~12  T>  T>  sJ2 

or  — -  =  -=^.     But  ^~  —  -=£-,  d  and  dl  being  the  diameters  of  the 
1  1C      flf  i  j^  C2       6?2 

conductors.     Substituting  the  value  of  — 1 ,  we  have  — -  =  — , 

-tv  \j  i      d\ 

and  C  :  Ci  =  d  :  dl9  which  shows  that  in  order  to  have  the 
same  loss  in  the  conductor  in  transmitting  a  given  amount  of 
energy,  the  diameters  of  the  conductors  must  be  directly  as 
the  currents  flowing  through  them.  But  the  weights  of  the 
wires,  and  hence  their  cost,  depend  upon  their  volumes, 
which  in  equal  lengths  are  to  each  other  as  the  squares  of  the 
diameters.  If  we  call  P  and  P!  the  prices  of  the  conductors 
per  unit  length,  we  shall  have  P  :  P!  =  d2 :  d\,  and  P  :  P1  = 
C2  :  d2 ;  or  the  cost  of  conductors  to  transmit  a  given  amount 
of  energy  with  the  same  loss  in  each  case  will  vary  as  the 
squares  of  the  currents  conveyed. 

The  importance  of  reducing  the  current  through  the  cir- 
cuit in  order  to  obtain  economy  in  distribution  is  very  fully 
recognized  by  electricians.  It  is  for  this  reason  that  arc-lamps 
are  placed  one  after  another,  or  "in  series,"  upon  a  circuit, 
and  that  incandescent  lamps  are  made  of  as  high  resistance 
as  possible.  Various  other  systems  besides  the  two  already 
described— the  series  and  multiple-arc — have  been  proposed 
with  a  view  of  increasing  the  economy  of  distribution,  but  we 
will  only  notice  two  here :  Mr.  Edison's  modification  of  the 
multiple-series  system,  and  the  induction-coil,  or  secondary 
generator  system. 


I.  EDISON'S  MULTIPLE-SERIES  SYSTEM  OF  DISTRIBUTION. 

As  we  have  previously  seen,  in  the  simple  multiple-arc 
system  of  distribution  each  lamp  requires  its  own  supply  of 
current,  so  that,  to  maintain  a  hundred  or  a  thousand  lamps, 
one  hundred  or  one  thousand  times  the  current  requisite  for 
one  lamp  must  be  transmitted  through  the  conductors.  If, 


356 


DISTRIBUTION   OF  ELECTRICITY. 


-0-1 


however,  the  lamps  be  arranged  so  that  there  are  two  or  more 
in  each  cross-circuit,  or  in  multiple-series  as  it  is  termed,  the 
supply  of  current  will  depend  not  upon  the  individual  lamp, 
but  upon  the  number  of  series  cross- circuits,  since  the  same 
current  goes  through  each  of  the  lamps  in  series,  in  succes- 
sion. Thus,  if  two  lamps  be  placed  in  series,  there  will  be 
required  but  one  half  the  current  for  a  given  number  that 
would  have  been  requisite  in  the  simple  multiple-arc  system. 
If  three  lamps  are  placed  in  series,  only  one  third  the  current 
will  be  required,  and  so  on.  The  electro-motive  force  must  of 
course  be  proportionately  increased  —  that  is,  it  must  be 
doubled  for  two  lamps  in  series,  trebled  for  three,  etc.  The 
disadvantage  of  this  arrangement  is,  that  the  lamps  are  not 
independent  of  each  other  ;  whenever  one  of  a  series  is  turned 
out,  all  of  that  series  must  be,  otherwise  the  remaining  lamps 
would  be  destroyed  by  the  increased  current  which  would 

then  flow  through  the 
cross  -  circuit  in  which 
they  are  placed.  Form- 
stance,  with  two  lamps 
in  series,  the  turning  out 
of  one  of  them  would 
reduce  the  resistance  of 
the  cross-circuit  to  one 
half.  Double  the  current 
would  then  flow  through 
it,  since  the  electro-mo- 
tive force  is  maintained 
constant.  With  three 
lamps  in  series,  the  cur- 
rent would  be  trebled 
when  two  are  extin- 
guished, etc.  To  render 
this  system  of  practical 
value,  therefore,  it  is 
necessary  to  make  each 
lamp  independent  of  the 
others,  as  in  the  simple 
multiple-arc  system.  This  Mr.  Edison  has  succeeded  in  doing 
in  the  manner  shown  in  Fig.  223,  which  represents  three  lamps 
arranged  in  series  on  each  cross-circuit.  The  dynamos  A,  A, 
A,  are  joined  together  in  series,  the  two  main  conductors,  P 


Or- 


Fio.  223.— Edison  multiple-series  distribution. 


ECONOMY   OF  CONDUCTORS. 


357 


and  N,  being  attached,  the  one  to  the  positive  pole  of  the 
first  machine,  and  the  other  to  the  negative  pole  of  the  last. 
Between  each  set  of  lamps,  compen- 
sating   conductors    (as    Mr.    Edison 
terms  them)  are  run  to  the  genera- 
tors, giving  an  arrangement  similar 
to  that  of  three  simple  multiple-arc 
circuits  placed  side  by  side. 

When  the  same  number  of  lamps 
are  in  each  multiple-arc  circuit,  no 
current  will  flow  through  the  com- 
pensating conductors,  but  it  will  pass 
from  the  positive  main  conductor 
through  each  cross-circuit  to  the  neg- 
ative one.  With,  however,  an  un- 
equal number  of  lamps  in  adjacent 
divisions,  the  excess  of  current  above 
that  necessary  for  the  smaller  number 
of  lamps  will  flow  through  the  com- 
pensating conductor  between  them. 
In  actual  construction  the  circuits 
will  be  arranged  so  that  the  number 
of  lamps  in  adjacent  divisions  will 
be  nearly  the  same  at  all  times.  The 
compensating  conductors  can  there- 
fore be  made  quite  small  and  inex- 
pensive. For  two  lamps  in  series 
Mr.  Edison  estimates  that  the  con- 
ductors will  need  to  be  but  thirty- 
eight  per  cent  of  the  size  required  for 
the  same  number  of  lamps  in  simple 
multiple-arc,  twenty -five  per  cent  for  the  main,  and  thirteen 
per  cent  for  the  compensating,  conductors.  The  application 
of  this  method  of  distribution  to  a  single  generator  is  shown 
in  Fig.  224.  In  this  case  the  compensating  conductor  is  con- 
nected with  an  extra  brush  on  the  machine,  placed  between 
the  other  two. 


FIG.  224.— Edison  multiple-series 
distribution  applied  to  one 
generator. 


II.   THE  SECONDARY-GENERATOR  SYSTEM  OF  DISTRIBUTION. 

In  this  system  the  lamps  or  other  apparatus  to  be  used  are 
placed  in  the  secondary  circuit  of  an  induction-coil,  the  pri- 


358  DISTRIBUTION  OF  ELECTRICITY. 

mary  wire  of  which  is  in  the  main  circuit.  As  the  tension 
and  intensity  of  the  secondary -circuit  current  may  be  made 
anything  desired  by  a  proper  winding  of  the  two  coils,  it  is 
possible  to  obtain  with  such  an  apparatus,  from  a  high-tension 
current  in  the  main  circuit,  currents  of  low  tension  and  con- 
siderable quantity  in  the  secondary.  Alternating  currents  are 
preferably  employed  in  operating  the  coils,  as  the  circuit- 
breaking  apparatus  may  then  be  dispensed  with.  The  induc- 
tion system  has  been  often  proposed,  and  variously  modified 
by  different  inventors,  but  has  been  so  far  but  very  little  used. 
It  was  patented  in  England  in  1857  by  Harrison,  and  was  em- 
ployed by  M.  Jablochkoff  in  1877  with  his  candles  and  his 
kaolin  incandescent  lamp,  already  described.  Mr.  J.  B.  Ful- 
ler proposed  the  system  in  1879,  and  arranged  his  secondary 
coils  so  that  they  could  be  coupled  in  tension  or  quantity, 
and  made  provision  for  varying  the  magnetic  strength  of  the 
iron  core.  The  system  was  also  used  by  Professors  Thomson 
and  Houston  for  operating  their  vibratory  arc-lamp,  and  an 
induction  system  has  been  patented  by  Mr.  Edison  in  which 
a  continuous  high-tension  current  in  the  main  circuit  produces 
a  continuous  current  of  low  tension  in  the  lamp  circuit.  None 
of  these  attempts  seem  to  have  passed  beyond  an  experimental 
stage,  but  in  the  early  part  of  last  year  the  system  was  revived 
in  England  by  Messrs.  Goulard  and  Gibbs,  who  have  put  it 
into  operation  in  the  London  underground  railway.  Their  ap- 
paratus does  not  differ  essentially  from  that  previously  used, 
though  they  construct  their  induction-coils  in  a  somewhat 
different  manner.  Each  circuit  consists  of  cables  containing 
a  number  of  wires,  which  cables  are  wound  about  a  central 
cylinder  in  the  way  in  which  the  wires  are  usually  wound. 
The  iron  core  is  composed  of  a  bundle  of  wires  placed  within 
a  brass  cylinder  by  the  withdrawal  of  which  the  secondary 
current  can  be  regulated,  and  consequently  the  amount  of  the 
light.  The  secondary  coil  is  divided  into  a  number  of  bob- 
bins, which  can  be  connected  in  tension  or  quantity,  so  as  to 
furnish  the  kind  of  current  desired.  A  number  of  these  in- 
duction-coils are  combined  into  one  apparatus  of  sufficient 
capacity  to  do  the  lighting  at  one  point — that  of  a  private 
house,  for  example— and  a  number  of  these  then  arranged  on 
the  circuit  one  after  another,  so  that  the  main-line  current 
goes  through  each  primary  coil  in  succession. 

The  practical  value  of  such  a  system  of  distribution  de- 


DIVISIBILITY   OF  THE  ELECTRIC   LIGHT.  359 

pends,  of  course,  upon  its  economy — whether  the  loss  occa- 
sioned by  the  transformation  of  the  high-tension  line  current 
into  others  of  low  tension  is  compensated  for  by  the  dimin- 
ished cost  of  the  conductors — in  which,  of  course,  must  be 
included  the  cost  of  the  induction  apparatus.  There  appears 
to  be  no  reason  why  the  generative  efficiency  and  the  electrical 
efficiency  should  not  be  good.  There  is  a  difficulty  in  placing 
inductive  apparatus  in  series  on  a  circuit,  as  the  work  done  in 
the  secondary  circuit  of  a  coil  directly  influences  the  current 
flowing  in  the  main  circuit,  and  hence  the  electrical  condition 
of  all  the  coils  on  the  same  main  line.  This  difficulty  does 
not,  however,  appear  to  be  insuperable.  In  long  circuits  the 
loss  due  to  an  alternating  current  would  possibly  be  consider- 
able, but  there  are  no  data  on  this  point.] 


CHAPTER  IY. 

DIVISIBILITY  OF  THE  ELECTRIC  LIGHT. 

[AT  the  time  when  attention  was  beginning  to  be  directed 
to  the  incandescent  light,  some  four  or  five  years  ago,  a  great 
deal  was  said  about  the  loss  of  light  resulting  from  division 
of  the  current,  and  the  difference  in  this  respect  between  gas 
and  electricity.  The  production  of  economical  burners  of  low 
candle-power  was  very  generally  spoken  of  as  a  solution  of 
the  problem  of  division,  as  if  there  was  in  some  special  sense 
a  problem  of  this  kind  in  the  case  of  electricity  quite  differ- 
ent from  that  presented  by  any  other  agent.  The  observed 
fact  was  simply  that  a  given  amount  of  electric  energy  yielded 
much  more  light  when  utilized  in  a  single  lamp  than  when 
divided  up  among  a  number  of  smaller  ones.  But  the  infer- 
ence which  was  apparently  drawn  from  it  was  the  very  curious 
one  that  the  power  necessary  to  maintain  a  number  of  lamps 
was  not  directly  proportional  to  their  number,  but  increased 
at  a  greater  rate.  This  inference  was  not  distinctly  stated, 
but  was  implied  in  much  that  was  written  on  the  subject,  by 
the  way  in  which  the  relation  between  small  and  large  lights 
was  presented.  As  the  notion  that  there  is  a  special  difficulty 
in  obtaining  subdivision  of  light  with  electricity  not  expe- 


360  DISTRIBUTION   OF  ELECTRICITY. 

rienced  with  other  means  of  illumination  has  not  yet  wholly 
disappeared,  it  may  be  worth  while  to  consider  the  reasons  of 
the  observed  difference  of  the  economy  of  large  and  small 
lights,  and  the  difference  between  gas  and  electricity  in  this 
respect. 

The  rate  at  which  energy  is  expended  in  an  electric  circuit 
is  measured,  as  we  have  already  seen,  by  the  product  of  the 
strength  of  the  current  by  the  electro-motive  force,  or  by  the 
square  of  the  current  by  the  resistance.  Suppose  we  take  a 
wire — say  ten  inches  long — and  pass  a  current  through  it  of 
sufficient  strength  to  bring  it  to  a  given  incandescence.  If 
this  current  be  denoted  by  C,  and  the  resistance  per  inch  of 
the  wire  by  R,  the  expenditure  of  electric  energy  in  the  wire 
per  second  will  obviously  be  10  C2  R.  Now,  if  this  wire  be 
divided  into  ten  parts,  and  these  be  arranged  on  a  circuit  one 
after  another,  the  expenditure  of  energy  will  evidently  be  the 
same.  If,  instead  of  placing  them  one  after  another,  or  "in 
series,"  they  are  arranged  side  by  side,  or  in  "multiple  arc," 
there  will  still  be  the  same  expenditure,  though  in  this  case 
the  relation  of  the  resistance  and  current  will  be  different. 
Each  of  the  inch-pieces  will  require  the  same  strength  of  cur- 
rent, C,  to  bring  it  to  its  previous  incandescence,  and,  as  its 
resistance  is  R,  the  expenditure  of  energy  will  be  C2  R,  and 
that  for  the  ten  wires,  10  C2  R.  Whichever  w-ay,  then,  these 
ten  pieces  of  wire  are  arranged,  they  require  precisely  the 
same  amount  of  power  to  maintain  them  at  a  given  incan- 
descence, and  it  is  quite  immaterial  (the  resistance  of  dis- 
tributing conductors  being  neglected)  whether  they  are  in- 
closed in  one  globe  or  each  in  a  separate  one,  and  thus  form 
ten  small  lamps  or  one  large  one.* 

It  appears  from  this  that  there  is  no  loss  whatever  by  sub- 
dividing the  current,  which  is  quite  true  so  long  as  the  other 
conditions  remain  unaltered.  The  amount  of  heat  generated 
by  a  given  expenditure  of  electrical  energy  is  a  definite  quan- 
tity depending  only  on  the  current  and  the  resistance,  and  is 
wholly  independent  of  the  number  of  centers  at  which  it  ap- 
pears, just  as  the  quantity  of  heat  generated  by  the  burning 
of  a  thousand  feet  of  gas  is  independent  of  the  number  of 
jets  in  which  it  is  burned.  The  temperature  to  which  a  body 

*  There  would  be  in  practice  a  difference  in  the  economy  of  the  one  long 
filament  and  the  ten  short  ones,  due  to  the  increased  loss  of  heat  by  the  latter 
by  conduction  through  the  supports. 


DIVISIBILITY  OF  THE  ELECTRIC  LIGHT.  361 

will  be  raised,  however,  by  this  amount  of  heat  depends,  as 
we  have  already  seen,  upon  the  relation  between  the  rate  of 
heat  generation  and  the  radiating  surface,  and  the  light  de- 
pends upon  the  temperature.  An  amount  of  heat-energy  suf- 
ficient to  produce  a  powerful  arc-light  may  be  expended  in 
such  a  manner — in  heating  a  long  copper  wire,  for  instance — 
as  to  produce  a  hardly  perceptible  rise  of  temperature,  and 
consequently  no  light  whatever.  Or  it  may  be  expended  in 
a  very  small  space,  with  the  production  of  a  high  temperature 
and  a  very  intense  light.  If  the  whole  of  the  energy  ex- 
pended in  the  ten-inch  wire  had  been  employed  in  heating 
one  of  the  small  inch-pieces,  the  lighting  effect  would  have 
far  surpassed  that  given  by  the  entire  wire  when  supplied 
with  the  same  amount  of  energy.  So  far  from  this  fact  being 
an  occasion  for  surprise,  it  would  be  very  remarkable  indeed 
if  there  was  a  different  result,  for  it  would  show  that  a  long 
wire  could  be  raised  to  as  high  a  temperature  by  a  given  heat- 
expenditure  as  a  short  one  of  the  same  diameter.  The  loss, 
then,  experienced  in  passing  from  one  powerful  to  many  feeble 
lights  is  a  loss  due,  not  to  the  mere  fact  of  division,  but  to  a 
.change  in  the  conditions  of  the  heat- supply  by  means  of  the 
division — to  a  lowering  of  the  rate  of  the  generation  of  heat 
per  unit  surface.  If  this  rate  be  kept  constant,  we  can  divide 
and  subdivide  indefinitely  without  any  loss  of  light  whatever. 
This  is  the  condition  realized  in  incandescent  lighting.  The 
unit  burner  may  be  multiplied  indefinitely,  and  the  power 
will  in  all  cases  be  directly  proportional  to  the  number  of 
lamps.  In  this  respect  there  is  no  difference  whatever  be- 
tween electric  lighting  and  gas-lighting.  The  observed  differ- 
ence between  the  results  obtainable  in  large  and  small  lights 
in  the  two  cases  is  a  difference  due  simply  to  the  temperatures 
which  can  be  reached  in  the  two  cases. 

With  electricity  the  limit  of  temperature  is  set  by  the  re- 
sistance of  the  incandescent  material  to  disintegration.  Car- 
bon is  so  refractory  that  this  limit  is  far  off,  and,  since  the 
light  yielded  by  an  incandescent  body  increases  very  rapidly 
with  the  temperature,  a  given  amount  of  electric  energy  ex- 
pended in  the  production  of  heat  in  a  small  space  is  able  to 
produce  a  great  amount  of  light.  When  this  heat  is  ex- 
pended over  a  larger  space — a  long  wire,  for  instance — the  tem- 
perature attainable  rapidly  decreases,  and  with  it  the  light. 

The  temperature  attainable  with  gas  is,  on  the  other  hand, 


362  DISTRIBUTION  OF  ELECTRICITY. 

limited  by  the  nature  of  the  combustible  and  the  point  of 
dissociation — the  point  at  which  the  chemical  affinity  of  a 
combustible  for  oxygen  begins  to  diminish,  so  that  combina- 
tion no  longer  takes  place,  and  an  increasing  portion  of  the 
combustible  gas  passes  off  unconsumed.  The  heat  generated 
by  the  combustion  of  a  given  amount  of  gas  can  not  therefore 
be  applied  so  as  to  raise  the  temperature  of  a  body  indefi- 
nitely, and  the  difference  between  the  total  lighting  effect, 
when  this  gas  is  consumed  in  many  small  burners  or  in  a  few 
large  ones,  is  consequently  much  less  marked  than  in  the  case 
of  electricity.  This  difference  may,  however,  be  considerable, 
as  recent  improvements  in  gas-burners  have  shown.  A  thou- 
sand feet  of  sixteen- candle  gas  burned  in  five-foot  burners 
will  give  thirty-two  hundred  candles,  while,  if  burned  in  fifty- 
foot  Siemens  burners,  it  will  yield  nine  thousand  candles. 

From  the  above  it  will  be  seen  that  the  ordinary  way  of 
presenting  the  relation  between  economy  of  large  and  small 
lights,  and  between  electricity  and  gas,  is  extremely  mislead- 
ing. The  electric  light  is  represented  as  suffering  a  loss  from 
which  gas-lighting  is  free,  while  the  fact  is  that  electricity  is 
able  to  attain  an  economy  not  realizable  with  gas.  The  proper 
statement  of  the  relation  of  the  two  illuminants  is  that,  with 
equal  expenditures  of  heat-energy,  you  can  get  a  much  greater 
amount  of  light  by  means  of  electricity  than  by  means  of  gas. 
The  electric  light  has  labored  under  the  disadvantage  of  an 
inversion  of  the  natural  order  of  development.  The  large 
light  was  produced  first  instead  of  last,  and  the  results  ob- 
tained with  it  have  furnished  the  standards  by  which  all 
others  were  judged.  Had  the  small  light  been  the  first  in  the 
order  of  production,  the  significance  of  the  superior  economy 
of  more  powerful  lights  would  have  been  readily  seen,  and 
incandescence  would  hardly  have  been  given  over  for  so  many 
years  as  hopelessly  uneconomical  because  it  fell  so  far  behind 
its  more  brilliant  competitor.  It  would  have  been  the  more 
readily  recognized  that  the  problem  of  incandescence  was 
concerned  simply  with  the  production  of  a  lamp  of  moderate 
intensity  which  should  be  as  economical  as  the  gas-flame  with 
which  it  would  have  to  compete,  and  that  the  difficulties  in 
the  way,  while  great,  were  surmountable.] 


ELECTRIC  METERS.  363 

CHAPTER  Y. 

ELECTRIC  METERS. 

[!N  any  commercial  electric  distribution,  by  which  the  con- 
sumer is  furnished  with  light  and  power  in  such  amounts  as 
he  desires,  some  means  of  measurement  must  be  provided. 
Though  electrical  quantities  are  capable  of  the  most  precise 
determination,  and  the  instruments  in  use  are  among  the  most 
accurate  which  the  physicist  possesses,  the  devising  of  a  prac- 
tical electric  meter  is  not  without  difficulties.  The  instru- 
ments of  the  physicist  measure  simply  the  amount  of  an 
electrical  quantity  at  a  time,  but  a  meter  is  required  to  do 
more  than  this — it  must  measure  the  expenditure  during  a 
certain  time.  As  that  which  the  consumer  is  required  to  pay 
for  is  not  electricity  simply,  but  work,  the  meter  must  either 
measure  the  work  done  directly,  or  measure  some  quantity 
from  which,  under  the  conditions  of  the  system  of  supply, 
the  work  can  be  determined.  In  instruments  of  the  first 
kind,  the  work  done  during  a  certain  time  may  be  obtained 
by  a  summation  of  that  performed  at  successive  instants,  and 
thus  be  given  by  a  single  measurement ;  or  it  may  be  obtained 
by  means  of  two  distinct  ones — the  one,  the  rate  at  which  work 
is  performed  at  each  instant,  and  the  other,  the  time  during 
which  it  has  continued.  In  instruments  of  the  second  class, 
the  aim  is  to  measure  the  quantity  of  electricity  simply  which 
has  passed  in  a  given  time.  This  may  be  done,  as  in  the  other 
class  of  meters,  by  a  summation  process,  or  by  a  double  meas- 
urement of  the  strength  of  the  current  flowing,  and  the  time 
during  which  it  flows.  The  summation  method  is  evidently 
the  more  accurate,  as  there  is  but  one  measurement,  and  con- 
sequently a  diminished  chance  of  error. 

One  of  the  simplest  instruments  involving  the  use  of  this 
method  for  the  measurement  of  the  amount  of  electricity  is 
the  voltameter,  or  depositing-cell.  As  is  well  known,  in  such 
a  cell  a  definite  amount  of  metal — zinc  or  copper — is  deposited 
upon  the  negative  plate  by  a  given  current.  If  the  current 
be  doubled  or  trebled,  or  if  the  same  current  be  continued 
twice  or  three  times  as  long,  there  will  be  twice  or  three  times 
the  deposit.  Each  additional  amount  of  electricity  passing 
through  the  cell  adds  its  own  deposit  to  that  already  existing, 


364 


DISTRIBUTION  OF  ELECTRICITY. 


so  that  at  the  end  of  any  given  time  it  is  only  necessary  to 
determine  the  amount  of  the  deposit  in  order  to  know  the 
quantity  of  electricity  which  has  passed  through  the  cell. 
This  method  is  the  one  used  by  Mr.  Edison  in  his  first  JSTew 


FIG.  225.— Edison  meter. 


York  district.  He  at  first  employed  copper,  but  these  have 
been  replaced  by  zinc,  depositing-cells.  The  zinc  plates  are 
made  of  as  pure  zinc  as  possible,  and  are  then  coated  with 
the  same  metal  by  electro-deposition,  after  which  they  are 


ELECTRIC  METERS.  365 

amalgamated.  Two  forms  of  meters  have  been  devised  by 
Mr.  Edison,  in  one  of  which  the  amount  of  deposited  metal 
is  automatically  registered,  and  in  the  other  of  which  this  is 
ascertained  by  weighing  the  electrodes  at  the  works  of  the 
company,  to  which  they  are  periodically  taken  by  the  meter 
inspectors.  This  latter,  which  is  the  one  actually  employed, 
is  shown  in  Fig.  225.  It  contains  two  cells,  the  indications  of 
one  of  which  serve  as  a  check  upon  those  of  the  other.  The 
latter  cell  is  examined  once  a  month,  the  zincs  taken  out  and 
replaced  by  fresh  ones.  The  indications  of  the  former  are 
taken  but  once  in  three  months,  the  agreement  of  the  two 
showing  the  accuracy  of  the  meter.  The  cells  are  each  placed 
in  circuits,  which  form  shunts  to  the  main  one,  so  that  only  a 
small  portion  of  the  total  current  passes  through  each,  and 
this  is  different  for  each  as  the  shunts  are  of  unequal  resist- 
ance. As  the  resistance  of  the  cell  varies  with  its  tempera- 
ture, provision  is  made  for  keeping  this  practically  constant 
by  means  of  a  lamp  inclosed  in  the  chamber  containing  the 
cells,  which  is  automatically  lit  when  the  temperature  falls 
too  low,  and  extinguished  when  it  rises  too  high,  by  means  of 
an  expansion-bar  closing  and  breaking  the  circuit  of  the  lamp. 

In  the  automatic  registering  meter,  shown  in  Fig.  226,  the 
weight  of  the  deposited  metal  successively  gained  by  the 
plates  is  caused  to  operate  a  counting  mechanism.  It  con- 
sists of  two  cells  placed  side  by  side,  constructed  so  that  the 
cell  itself  forms  one  plate,  the  other  being  hung  in  the  liquid 
from  the  scale  beam.  The  electrical  connections  are  made  so 
that  the  current  goes  from  the  plate  forming  the  jar  to  that 
suspended  plate  which  is  raised  in  one  cell,  and  from  the  low- 
ered suspended  plate  to  the  enclosing  jar  in  the  other  cell. 
The  raised  plate  is  consequently  gaining  in  weight,  and  the 
lowered  losing.  When  the  raised  plate  becomes  the  heavier 
of  the  two,  it  descends,  and  the  current  is  reversed.  There 
is  therefore  a  successive  gain  and  loss  of  weight  by  the  sus- 
pended plates  which  causes  the  scale-beam  to  periodically 
oscillate,  each  movement  of  which  acts  upon  the  registering 
apparatus.  The  dials  are  constructed  to  show,  not  the  amount 
of  electricity  in  electrical  measure,  but  the  equivalent  of  the 
amount  of  gas  necessary  to  give  the  light  which  has  been  fur- 
nished by  the  company. 

Current  meters,  which  record  the  amount  of  electricity  by 
the  employment  of  the  summation  method,  have  also  been 


366  DISTRIBUTION  OF  ELECTRICITY. 

designed  by  Mr.  C.  Yernon  Boys  and  Dr.  Hopkinson.  In 
Mr.  Boys's  meter,  the  current  is  applied  so  as  to  maintain  a 
pendulum  in  vibration.  The  impulses  are  given  to  the  pen- 
dulum by  means  of  the  attraction  of  an  electro-magnet,  and, 
since  the  force  required  to  move  a  pendulum  varies  as  the 
square  of  the  rate  of  vibration,  and  the  attraction  of  a  mag- 
net varies  as  the  square  of  the  current  flowing  around  it, 


FIG.  226. — Edison  meter,  with  registering  apparatus. 

the  rate  of  vibration  will  be  proportional  to  the  current  flow- 
ing. By  means  of  simple  mechanism,  the  number  of  vibra- 
tions can  be  registered,  so  that  this  arrangement  can  be  read- 
ily made  to  record  the  amount  of  electricity  which  has  passed 
in  a  given  time. 

In  Dr.  Hopkinson's  device,  the  measurement  is  effected  by 
overcoming  the  attraction  of  an  electro-magnet  by  centrifugal 
force,  the  parts  being  arranged  so  that  the  speed  of  a  little 


ELECTRIC  METERS.  367 

electro-motor  is  proportional  to  the  current  flowing.  The 
electro-motor  is  placed  in  a  shunt  circuit,  and  drives  a  verti- 
cal shaft,  upon  which  is  mounted  an  ordinary  ball-governor, 
which  is  connected  with  the  armature  of  an  electro-magnet, 
so  that  it  raises  this  against  the  pull  of  the  magnet  as  the 
balls  are  thrown  out  under  the  influence  of  centrifugal  force. 
This  electro-magnet  is  placed  in  the  main  circuit,  and  its 
strength  therefore  depends  upon  that  of  the  current  flowing 
through  this  circuit.  With  this  arrangement  it  is  evident 
that,  when  only  a  small  current  is  circulating  in  the  coils  of 
the  magnet,  a  low  speed  of  the  governor  will  be  sufficient  to 
overcome  its  attraction  and  draw  away  its  armature.  As  the 
current  increases,  it  takes  a  higher  speed  of  the  governor  to 
do  this,  so  that  there  is  a  definite  relation  between  the  speed 
at  which  the  motor  will  rotate,  when  there  is  a  balance  be- 
tween the  magnetic  attraction  and  the  centrifugal  force,  and 
the  current  flowing.  Since  the  centrifugal  force  varies  as  the 
square  of  the  speed,  and  the  magnetic  attraction  as  the  square 
of  the  current  circulating  in  its  coils,  this  speed  of  the  motor 
will  be  directly  proportional  to  the  current.  In  order  that  the 
motor's  speed  should  always  be  maintained  against  the  op- 
posing force  of  the  electro-magnet,  and  therefore  indicate  the 
strength  of  the  current,  the  motor  circuit  is  interrupted  when 
the  centrifugal  force  overbalances  the  magnetic  attraction. 
The  speed  of  the  motor  therefore,  decreases  until  the  armature 
descends  and  this  circuit  is  again  closed.  The  number  of  rev- 
olutions which  have  taken  place  in  a  given  time  evidently 
measure  the  quantity  of  electricity  which  has  passed  in  this 
time. 

A  quite  simple  current-meter,  of  the  class  in  which  there 
is  a  measurement  of  both  the  current  flowing  and  the  time 
which  it  continues,  has  been  designed  by  M.  Cauderay.  The 
needle  of  an  ampere-meter  (a  special  form  of  galvanometer)  is 
placed  so  that  it  stands  vertically  in  front  of,  and  but  a  short 
distance  from,  a  small  roller,  provided  with  projecting  pins, 
similar  to  the  barrel  of  a  music-box.  These  pins  are  arranged 
in  circles  around  the  roller,  the  successive  circles  each  way 
from  the  center  containing  a  greater  number.  The  central 
circle  has  no  projection,  so  that  when  the  needle  is  vertical 
the  cylinder  can  rotate  without  touching  it.  If,  however,  the 
needle  is  deflected  to  one  side  or  the  other  so  as  to  incline 
from  the  vertical,  its  point,  which  is  formed  of  a  triangular 

25 


368  DISTRIBUTION   OF  ELECTRICITY. 

piece  of  brass,  will  be  pressed  out  slightly  by  the  projecting 
pins  in  the  circle  which  it  is  opposite.  Each  movement  of 
this  kind  causes,  through  appropriate  mechanism,  the  motion 
of  the  hand  of  a  dial  similar  to  that  used  in  gas-meters.  As 
the  extent  to  which  the  needle  is  drawn  aside  depends  upon 
the  strength  of  the  current  flowing  through  the  ampere-meter, 
it  is  evident  that,  if  the  cylinder  be  turned  at  a  constant  rate, 
this  arrangement  will  measure  the  amount  of  electricity  which 
has  passed  in  a  given  time.  It  will  be  perceived  that  the  ac- 
curacy of  this  measurement  depends  on  that  of  two  distinct 
pieces  of  apparatus — the  current  indicator  and  the  revolving 
drum — and  that  there  is  therefore  a  double  chance  of  error. 
Both  the  speed  of  the  drum  and  the  accuracy  of  the  ampere- 
meter can  be  very  easily  tested  and  regulated  when  found  to 
be  wrong,  however,  so  that  the  instrument  can  be  readily 
kept  sufficiently  accurate  for  all  practical  purposes.  In  the 

type  designed  for  incandescent 
lighting,  it  is  the  intention  to 
construct  the  meters  to  work 
with  definite  differences  of  po- 
tential between  the  terminals, 
the  mechanism  being  so  arranged 
that  the  meter  ceases  to  register 
if  the  electro-motive  force  falls 
below  a  certain  limit.  The  im- 

.  227.— Mr.  Boys'  work-meter.        portance  of  this  will  be  readily 

seen  when  it  is  remembered  that 

by  a  slight  decrease  in  the  current  through  the  lamp  the  light 
may  be  very  greatly  diminished,  while  the  wrork  done,  for 
which  the  consumer  would  have  to  pay,  would  be  but  little 
less  than  when  the  lamp  is  giving  its  normal  light. 

Work-meters  have  been  designed  by  Mr.  Boys,  whose  cur- 
rent-meter has  been  described  above,  and  by  Professors  Ayr- 
ton  and  Perry.  Mr.  Boys's  meter  belongs  to  the  class  above 
indicated,  in  which  the  total  work  done  during  a  time  is 
given  by  a  process  of  summation  or  integration.  The  prin- 
ciple of  its  operation  is  shown  in  Fig.  227.  A  small  wheel, 
mounted  like  a  caster,  so  that  it  can  swing  around  a  vertical 
axis  as  well  as  revolve  on  its  own,  is  pressed  against  a  roller 
or  cylinder  free  to  turn  on  its  axis.  Under  these  conditions, 
if  the  wheel  is  inclined  to  the  axis  of  the  cylinder,  and  the 
cylinder  be  drawn  under  it  in  the  direction  of  its  length,  the 


ELECTFJO  METERS.  369 

wheel  will  swing  so  as  to  stand  lengthwise  of  the  cylinder. 
But  if  the  wheel  be  held  in  its  inclined  position,  the  cylinder 
will  rotate,  and  the  number  of  its  revolutions,  while  being 
moved  its  own  length,  will  depend  upon  the  amount  of  the 
inclination.  Now,  it  will  require  force  to  hold  the  wheel  in- 
clined while  the  cylinder  is  dragged  under  it,  and  this  force 
will  clearly  be  greater  as  the  amount  of  inclination  is  in- 
creased. The  cylinder  will  also  pull  the  wheel  around  in 
the  direction  of  its  movement  the  more  strongly  as  its  move- 
ment is  more  rapid.  The  force  required  to  incline  the 
wheel,  multiplied  by  the  distance  through  which  the  cylin- 
der turns,  will  evidently,  therefore,  be  a  measure  of  the  work 
done,  and,  if  we  know  the  work  represented  by  one  turn  of 
the  cylinder,  the  number  of  revolutions  will  give  the  total 
work  performed  in  a  given  time.  It  will  be  observed  that 
it  is  not  necessary  to  move  the  cylinder  at  any  definite  rate, 
since  the  same  work  will  be  done  when  the  cylinder  moves 
rapidly  and  the  wheel  is  at  a  small  inclination  as  w^hen  the 
wheel  is  at  a  great  inclination  and  the  cylinder  moves  more 
slowly.  This  apparatus  may  be  readily  adapted  to  measure 
the  work  done  by  an  electric  current,  by  inclining  the  wheel 
by  magnetic  attraction  and  moving  the  cylinder  under  it  by 
means  of  clockwork.  Work  must  be  done  by  the  current 
to  maintain  the  wheel  in  its  angular  position,  which  w^ork 
will  be  measured  by  the  number  of  rotations  of  the  cylinder. 
In  Mr.  Boys's  arrangement,  the  cylinder  is  given  a  sort  of 
mangle-motion,  by  which  it  travels  forward  in  contact  with 
one  wheel  and  backward  in  contact  with  another  on  its  oppo- 
site side,  the  object  of  this  construction  being  to  obtain  a 
continuous  revolution  of  the  cylinder.  The  inclination  of  the 
wheels  is  obtained  by  means  of  an  arrangement  of  solenoids 
traversed  by  the  current  to  be  measured. 

In  the  work-meter  of  Professors  Ayrton  and  Perry,  the 
work  is  obtained,  not  by  a  direct  measurement  of  it,  but  from 
the  amount  of  deviation  from  the  normal  working  of  an  ap- 
paratus produced  by  it.  If  we  have  a  clock  keeping  time 
accurately,  it  may  be  made  to  gain  or  lose  time  by  impulses 
given  to  its  pendulum.  To  change  the  rate  of  vibration  of  a 
pendulum,  however,  requires  work,  and  the  total  amount  of 
work  performed  in  a  given  time  will  evidently  be  measured 
by  the  amount  of  correction  needed  by  the  clock.  In  the 
instrument  of  Professors  Ayrton  and  Perry,  the  control  of  the 


370  DISTRIBUTION  OF  ELECTRICITY. 

clock  is  effected  very  simply  by  means  of  two  solenoids,  one 
of  fine  and  the  other  of  coarse  wire.  The  fine-wire  coil  takes 
the  place  of  the  ordinary  pendulum -bob,  and  is  placed  in  a 
shunt  circuit,  which  forms  a  bridge  between  the  mains  when 
the  arrangement  of  the  lamps  is  in  multiple  arc,  and  is  con- 
nected with  the  main  wire,  where  it  enters  and  leaves  the 
house,  when  the  devices  are  arranged  in  series.  The  current 
flowing  through  this  coil,  therefore,  depends  upon  the  differ- 
ence of  potential  between  its  ends,  and  consequently  indi- 
cates the  potential  of  that  furnished  to  the  house.  The 
coarse-wire  coil  is  in  the  main  circuit,  and  has,  therefore, 
the  current  supplied  to  the  house  flowing  through  it.  It  is 
fixed  to  the  frame  of  the  clock  directly  behind  the  moving 
fine-wire  coil.  The  attraction  between  these  two,  therefore, 
varies  as  the  current  and  potential  supplied  to  the  house — 
that  is,  as  the  power — and  the  amount  which  the  clock  loses 
in  a  given  time  is  proportional  to  the  power  supplied.  The 
correctness  of  the  indications  of  this  meter  evidently  depend 
upon  the  accuracy  of  the  clock,  but,  as  clocks  which  are  good 
time-keepers  can  be  readily  obtained,  and  at  a  comparatively 
small  cost,  this  objection  does  not  appear  to  be  of  much  mo- 
ment.] 


BOOK    VI. 
APPLICATIONS   OF  THE   ELECTRIC   LIGHT. 


CHAPTER  I. 

ELECTRICITY  IN  LIGHT-HOUSES. 

IT  is  in  light-houses  that  the  electric  light  found  its  first 
important  application.  The  luminous  intensity  that  it  could 
attain  enabled  the  range  of  the  light  to  be  considerably  in- 
creased, not  only  to  that  necessary  for  clear  weather — this 
had  already  been  attained  for  a  long  time  by  the  powerful 
lamps  in  use — but  to  that  required  in  times  of  storm.  Against 
the  storms  there  is,  in  fact,  no  other  resource  than  to  augment 
to  its  utmost  the  brightness  of  the  focus,  and  this  resource 
was  often  insufficient. 

At  the  present  day,  when  steam  has  rendered  voyages  so 
frequent  and  so  easy,  there  are  few  persons  who  do  not  know 
what  a  light-house  is,  and  who  have  not  seen  at  night  with 
interest  those  brilliant  stars  which  mean  lights  upon  the  coast 
and  on  reefs  to  warn  mariners  at  a  distance,  to  indicate  to 
them  their  position,  and  to  guide  them  into  ports.  But  this 
knowledge  generally  goes  but  little  further,  and  we  do  not 
think  it  useless  to  add  to  it  such  explanations  as  will  make 
better  understood  the  progress  which  the  use  of  the  electric 
light  in  so  important  a  service  represents. 

The  origin  of  light-houses  goes  back  to  the  beginning  of 
navigation,  of  which  they  were  indispensable  auxiliaries. 
Homer  described  in  the  "Iliad"  the  use  of  fires  lighted  at 
night  on  the  rocks  to  direct  the  galleys  of  the  Greeks  ;  but 
the  first  light-house  properly  so  called  is  that  which  was  built 
by  a  king  of  Egypt  300  years  before  the  Christian  era,  oppo- 
site the  port  of  Alexandria,  on  an  island  called  Pharos,  whence 
doubtless  comes  the  name  which  has  been  given  them,  phare. 


372  •    APPLICATIONS  OF  THE  ELECTRIC  LIGHT. 

It  was  a  tower  of  masonry  seventy-five  feet  in  height,  on 
whose  summit  there  was  maintained  an  enormous  bonfire. 
This  primitive  mode  of  lighting  remained  for  a  long  time  the 
only  one  employed  ;  sometimes  large  oil-lamps,  with  dipping 
wick — the  only  ones  known  at  this  epoch — were  substituted 
for  it.  In  1727,  under  Louis  XV,  it  became  necessary  to  re- 
place by  an  iron  grate  the  ancient  masonry  fireplace  of  the 
tower  of  Cordouan,  built  at  the  mouth  of  the  Gironde,  to  hold 
the  fire  when  bituminous  coal  began  to  take  the  place  of  wood 
as  a  combustible. 

Attempts  had  also  been  made  to  use  lamps  with  reflectors, 
and  an  apparatus  composed  of  eighty  lamps  had  been  estab- 
lished in  1782  upon  this  same  tower  of  Cordouan  ;  but  it  was 
very  imperfect,  and  the  navigators  had  immediately  demanded 
a  return  to  the  old  coal-fire.  The  first  real  improvements  date 
from  the  invention  of  the  lamp  with  double  air-draught  by 
Argand,  and  from  that  of  parabolic  mirrors  by  a  French  en- 
gineer named  Teulere.  In  the  year  1793  they  were  utilized  in 
the  construction  of  an  apparatus  formed  of  three  groups  of 
four  lamps  each ;  these  groups  were  spaced  so  as  to  divide 
the  circumference  into  three  equal  parts,  supported  by  a 
frame,  which  a  machine,  regulated  by  a  pendulum,  turned 
around  every  six  minutes.  Thus,  every  two  minutes,  succes- 
sive flashes  of  extreme  brightness,  which  lasted  six  seconds, 
were  obtained.  This  was  a  considerable  progress,  and  all  the 
marine  powers  hastened  to  adopt  it. 

These  apparatus  are  called  catoptric,  because  the  concen- 
tration of  the  luminous  rays  emanating  from  the  lamps  is 
obtained  by  simple  reflection.  Except  in  size  and  some  few 
details  of  construction,  those  which  are  used  to-day  corre- 
spond with  the  apparatus  of  Teuldre. 

This  solution  was  insufficient,  because  of  the  impossibility 
of  giving  to  the  mirrors  suitable  dimensions  without  rendering 
them  much  too  difficult  to  construct,  and  too  heavy  to  move. 
Recourse  was  therefore  had  to  grouping  together  a  large 
number  with  a  lamp  for  each  one,  but  then  there  was  always 
a  limit  to  the  intensity  of  the  lights.  In  fact,  and  this  is 
often  lost  sight  of,  it  is  elevation  of  temperature  that  increases 
the  luminous  radiation ;  the  concentration  of  a  number  of 
lights  upon  any  one  point  only  augments  the  illumination  of 
this  surface,  without  increasing  in  the  same  proportion  the 
extent  of  the  surface  or  the  luminous  range  of  the  group 


ELECTRICITY  IN  LIGHT-HOUSES.  373 

thus  constituted.  Besides,  the  aberration  inseparable  from 
this  mode  of  reflection  renders  useless  the  increasing  of  lights 
in  the  group  beyond  a  comparatively  restricted  limit. 

It  was  at  this  juncture  that  Augustin  Fresnel  thought  of 
utilizing  for  light-house  apparatus  the  property  of  convex 
lenses,  refracting,  parallel  to  their  axis,  rays  of  light  emanat- 
ing from  their  principal  focus ;  he  invented  dioptric  appa- 
ratus. On  account  of  the  difficulty  which  the  manufacture 
of  glass  lenses  thick  enough  for  his  needs  would  have  pre- 
sented, Fresnel  first  thought  of  making  them  of  hollow  blown 
glass,  containing  water  or  alcohol.  Such  lenses  would  not 
have  been  easy  to  construct  and  preserve.  Fresnel  thought 
of  overcoming  their  excessive  thickness  by  composing  his 
lenses  of  a  central  part,  surrounded  by  concentric  rings,  one 
projecting  over  the  top  of  the  other,  and  so  to  say  represent- 
ing a  series  of  lenses  of  different  radii,  but  with  one  common 
principal  focus  ;  it  was  the  lens  with  ridges,  of  which  Buff  on 
seems  to  have  had  the  conception  in  advance  of  him,  and 
without  his  knowing  it ;  but  he  could  not  construct  it  as  he 
conceived  of  it  as  made  in  one  piece,  whereas  Fresnel  made 
it  of  separate  pieces,  molded  and  ground  separately,  and  then 
accurately  put  together. 

As  there  was  no  chance  of  placing  several  lamps  in  the 
center  of  such  an  apparatus,  Fresnel  and  Arago,  taking  up 
again  an  idea  of  Rumford,  succeeded  in  constructing  lamps 
with  several  concentric  wicks,  quite  close  together,  and  sepa- 
rated by  as  many  annular  currents  of  air.  The  flanies  heating 
each  other  mutually,  the  general  temperature  is  higher,  and 
the  light  becomes  white  and  brilliant.  An  excess  of  oil  is 
caused  to  flow  to  the  wicks,  to  retard  their  carbonization  and 
cool  the  burners.  In  this  manner  lamps  for  vegetable  oil  are 
constructed  that  contain  four  wicks,  and  give  three  or  four 
times  the  amount  of  light  given  by  the  largest  parabolic  re- 
flectors ;  besides,  the  Fresnel  lenses  only  absorb  at  most  five 
per  cent  of  the  total  light,  while  the  best  reflectors  absorb  fifty 
per  cent  of  it.  With  this  system  it  becomes  easy  to  arrange  all 
combinations  of  lenses  necessary  to  give  to  the  different  lamp- 
flames  the  particular  character  that  is  necessary.  Fresnel 
completed  his  invention  by  utilizing  another  property  of  glass 
rings  of  triangular  cross-section — that  is  to  say,  refraction 
and  total  reflection — he  thus  constructed  rings  called  cata- 
dioptric,  which  utilize  the  rays  that  could  not  be  caught 


374  APPLICATIONS  OF  THE  ELECTRIC  LIGHT. 

by  the  dioptric  drum  without  unduly  exaggerating  its  di- 
mensions. 

Once  more  it  was  on  the  light-house  tower  of  Cordouan 
that  the  first  apparatus  of  this  sort  was  established  in  1822, 
after  the  edifice  had  been  increased  in  height  so  as  to  bring 
the  lantern  sixty  metres  above  the  level  of  the  sea. 

Since  this  epoch,  thanks  to  the  labors  of  Messrs.  Doty  and 
Denechaux,  mineral  oil  can  now  be  used  without  inconven- 
ience of  any  sort,  so  that  a  fifth  wick  can  be  added  to  lamps 
of  the  first  order,  and  so  on.  The  light  was  increased  with- 
out any  great  augmentation  in  the  expense.  Gas  itself  has 
been  used,  and  with  it  most  of  the  Scotch  light-houses  are 
illuminated. 

For  a  long  time  the  electric  light  was  thought  of  for  this 
use  ;  but  such  a  service  must  be  characterized  by  absolute 
regularity  and  certainty ;  the  electricity  must  be  produced 
by  sufficiently  powerful  machines,  and  as  perfect  an  appa- 
ratus as  possible  must  be  used  for  regulating  the  voltaic  arc. 
It  is  to  the  machine  of  Nollet,  named  the  Alliance,  and  Ser- 
rin's  regulator,  that  the  honor  belongs  of  having  caused,  in 
1864,  the  adoption  of  the  electric  light  in  the  light-houses  of 
France,  under  the  skillful  direction  of  the  inspector-general, 
Reynaud.  It  had  in  like  manner  been  applied,  in  1862,  to 
the  English  light-house  of  Dungeness,  with  a  Holmes  machine 
(a  copy  of  the  Alliance  machine),  and  a  regulator  identical 
with  that  of  Serrin. 

Although  electricity  had  fulfilled  all  the  promises  it  had 
ever  given,  its  use  did  not  extend  very  rapidly,  and  in  1881 
there  were  only  twelve  light-houses  thus  lighted  in  the  whole 
world — four  in  France,  six  in  England,  one  in  Russia,  and  the 
last  at  Port  Said,  at  the  entrance  of  the  Suez  Canal.  The 
state  of  the  case  is,  that  the  service  of  coast-lighting,  obliged 
to  follow  the  progress  of  navigation,  could  not  wait  for  the 
last  improvements  in  electricity,  and  that  when  the  electricity 
at  last  was  ready,  all  the  light-houses  that  were  necessary  and 
possible  were  already  supplied  with  optical  apparatus  con- 
structed to  receive  the  61d  oil-lamps.  All  these  apparatus 
would  have  to  be  sacrificed,  and  after  this  a  still  greater  ex- 
pense would  follow  ;  for  this  reason  the  general  use  of  it  has 
been  postponed  to  the  time  when  these  apparatus  would  be 
naturally  replaced.  In  France,  in  consequence  of  the  exami- 
nations and  proposals  presented  in  January,  1880,  by  the 


ELECTRICITY  IN  LIGHT-HOUSES.  375 

director  of  the  light-house  service,  M.  Allard,  forty-two  oil 
light-houses  are  to  be  transformed  successively  into  electric 
light-houses.  In  England,  the  proposal  is  to  establish  one 
hundred.  Similar  examinations  are  being  pursued  in  the 
United  States,  Australia,  and  even  in  Turkey. 

It  is  important  to  remark  that,  in  spite  of  the  common  ex- 
pression, lighting  the  coasts  (eclairage  des  cotes\  light-houses 
do  no  lighting  in  the  proper  acceptation  of  the  word.  Their 
role  is  to  be  visible  at  the  greatest  possible  distance,  and  this 
distance,  which  is  called  their  range,  depends  on  the  height 
of  the  lantern  above  the  horizon  and  on  its  luminous  inten- 
sity. Thus  geographic  range  should  be  distinguished  from 
luminous  range. 

The  first  is  limited  by  the  roundness  of  the  earth ;  it  is 
equal  to  the  length  of  a  line  carried  from  the  lantern  tangen- 
tially  to  the  spherical  surface  of  the  sea,  and  prolonged  until 
it  reaches  the  eye  of  the  observer  ;  this  last  is  naturally  sup- 
posed to  be  at  the  greatest  height  attainable  on  the  mast  of 
the  ship  ;  by  being  elevated  from  three  to  twenty  metres  it  is 
capable  of  increasing  the  distance  some  ten  kilometres.  Un- 
fortunately, the  height  of  the  lantern  is  always  limited  by  the 
difficulties  of  construction  ;  the  highest  light-houses  are  those 
placed  where  the  formation  of  the  coast  makes  it  possible  to 
lay  their  foundations  successfully  in  places  already  elevated 
high  above  the  sea-level,  such  as  those  of  Agde  and  Cape 
Camarat,  in  the  Mediterranean,  which  are  126  and  130  me- 
tres above  the  sea-level,  and  whose  geographic  range  attains 
the  very  unusual  extent  of  50  and  51  kilometres.  When  this 
advantage  can  not  be  had,  they  rarely  exceed  60  metres  in 
height  and  30  to  36  kilometres  of  geographic  range,  like  the 
Cordouan  light-house  in  its  present  state. 

With  a  powerful  enough  lamp,  the  luminous  range  can 
attain,  and  even  exceed,  the  length  of  the  geographic  range, 
but,  unfortunately,  in  clear  weather  only ;  it  rapidly  dimin- 
ishes on  many  occasions  with  the  transparency  of  the  air, 
and,  as  we  shall  see,  this  diminution  has  to  be  taken  into 
account  in  calculating  the  distances  to  be  allowed  between 
light-houses. 

As  a  first  service,  light-houses  are  expected  to  indicate  to 
the  mariner  his  approach  to  coasts,  and  this  at  as  great  a  dis- 
tance as  possible.  Those  used  for  this  purpose  should  be  of 
the  highest  luminous  intensity  ;  they  are  the  light-houses  of 


376  APPLICATIONS  OF  THE  ELECTEIC  LIGHT. 

the  first  order )  to  which  also  is  given  the  name  of  pliares  de 
grande  alienage .  If  the  navigator  is  deceived,  or  has  de- 
viated from  his  course  in  bad  weather,  he  must  be  able  to  fol- 
low the  coast-line,  at  a  safe  distance,  until  he  reaches  a  point 
in  front  of  his  harbor.  He  must  then  be  able  to  find  an  unin- 
terrupted succession  of  lights  of  the  same  power,  not  losing 
sight  of  one  before  finding  the  next  one  ;  in  a  word,  the  cir- 
cles of  luminous  range  of  light-houses  must  reciprocally  in- 
tersect at  a  good  distance  from  shore,  and,  in  order  that  this 
may  take  place  as  often  as  possible,  there  must  be  adopted 
for  the  radius  of  these  circles  the  luminous  range  that  cor- 
responds to  the  mean  degree  of  transparency  of  the  atmos- 
phere— that  is  to  say,  that  which  is  reached  or  exceeded  half 
the  time.  Rigorous  observations  carried  on  for  years  have 
established  this  factor  for  different  parts  of  the  coasts ;  it  is 
greater  in  the  Mediterranean  than  on  the  shores  of  the  ocean 
or  of  the  English  Channel. 

Having  reached  the  desired  spot,  the  mariner  should  be 
able  to  approach  closer  to  the  coast  without  danger,  and  it 
becomes  necessary  to  indicate  to  him  by  a  new  system  of 
lights  the  dangers  he  may  meet  in  this  second  zone.  Hence 
comes  the  necessity  of  employing,  back  of  the  first  light- 
houses, other  lights  of  various  intensities  corresponding  to 
the  second,  third,  fourth,  and  even  fifth  order.  Finally,  less 
powerful  lights  give  him  the.  last  ranges  to  follow  to  enter 
port  at  night ;  these  are  the  range-lights.  In  the  sea-ports, 
lights  of  different  colors  show  him  at  every  hour  of  the  night 
the  depth  of  water  in  the  port  at  each  change  of  level  of  fifty 
centimetres. 

Naturally,  all  light-houses  do  not  have  to  distribute  their 
rays  around  them  in  the  same  way :  the  large  mainland  lights, 
and  sometimes  light-houses  of  the  second  order,  must  light 
the  whole  horizon  ;  others  only  light  a  larger  or  smaller  seg- 
ment, and  the  light  which  would  be  useless  on  the  landward 
side  is  reflected  seaward.  When  the  transparence  of  the  air 
becomes  so  diminished  that  the  circles  of  the  luminous  range 
of  the  mainland  lights  no  longer  intersect,  the  lights  of  the 
second  line  fill  the  void,  and  prevent,  as  far  as  possible,  the 
danger  which  would  result  therefrom ;  in  practice  this  hap- 
pens during  about  six  months  of  the  year  ;  during  the  other 
months  the  mariner  only  receives  warning  at  a  distance  which 
is  the  smaller  as  the  atmosphere  is  less  transparent,  and  here 


ELECTRICITY  IN  LIGHT-HOUSES.  377 

will  be  one  of  the  advantages  of  the  electric  light,  in  reducing 
this  period  to  two  months  at  the  most  on  the  Atlantic  coast, 
and  to  one  month  on  the  Mediterranean,  on  account  of  the 
increase  of  luminous  range. 

In  order  that  the  indications  they  afford  the  mariner  may 
be  very  clear,  it  is  indispensable  that  all  these  successive 
lights  present  different  and  well-defined  characteristic  appear- 
ances. To  attain  this  end,  five  varieties  of  lights  are  used : 
simple  fixed  light,  double  fixed  light,  eclipse-light,  with  flashes 
every  thirty  seconds ;  eclipse-light,  with  flashes  every  min- 
ute ;  fixed  light,  varied  by  four-minute  flashes.  As  complete 
eclipses  make  it  hard  to  again  find  the  light,  especially  in  bad 
weather,  in  the  French  light-houses  a  fixed  light  is  maintained 
during  the  time  of  eclipse,  so  that  the  light-house  can  be 
kept  in  view.  This  fixed  light  is  relatively  weaker,  and  varies 
in  value  between  one  half  and  one  seventh  of  the  intensity  of 
the  regular  light,  according  to  whether  it  is  composed  of  rays 
taken  from  the  top  and  bottom  of  the  apparatus,  or  of  those 
taken  from  the  bottom  only. 

These  five  characters  not  proving  enough,  they  were  sup- 
plemented by  the  color  of  the  lights,  in  spite  of  the  loss  of 
intensity  resulting  therefrom,  because  a  colored  light  is  one 
that  has  lost  a  part  of  its  luminous  rays.  Furthermore,  only 
green  and  red  can  be  used,  and  the  last  as  seldom  as  possible. 
In  this  way  there  are  obtained  fixed  lights  varied  by  red  and 
green  flashes  every  four  minutes,  and  lights  composed  of 
white  and  red  flashes.  These  are  the  different  characters 
used  in  actual  light-houses  using  oil-lamps ;  their  defect  is 
too  long  a  period  of  manifestation,  forcing  upon  the  mariner 
a  long-sustained  attention  to  recognize  the  character  of  the 
light  he  has  sighted.  A  certain  skill  even  is  necessary  to  ap- 
preciate differences  of  only  one  half  minute.  They  were 
adopted  because  of  the  difficulty  of  imparting  to  the  old  ap- 
paratus, large  and  clumsy,  a  somewhat  rapid  movement  of 
rotation. 

As  the  dimensions  of  optical  apparatus  depend  upon  the 
volume  of  the  sources  of  light  whose  rays  they  concentrate, 
the  great  reduction  in  volume  obtained  by  the  use  of  the 
electric  light  makes  it  possible  to  reduce  the  size  of  the  op- 
tical apparatus.  The  diameter  of  oil-lamp  apparatus  of  the 
first  order,  which  was  1*84  metre,  can  be  reduced  to  *5  or 
•6  metre  for  electric  lights  of  the  same  order.  The  extreme 


378  APPLICATIONS   OF  THE  ELECTRIC  LIGHT. 

lightness  of  these  new  optical  apparatus  makes  it  possible  to 
turn  them  much  faster ;  thus,  a  new  character  of  light,  called 
scintillating,  can  be  adopted.  To  produce  it,  a  fixed-light 
apparatus  is  used  which  normally  concentrates  rays  in  a  ver- 
tical plane ;  around  this  apparatus  a  drum  of  lenses,  called 
vertical-element  lenses,  is  caused  to  rotate.  These  lenses  are 
plates  of  glass,  having  a  lenticular  section,  the  same  through- 
out their  length.  Each  of  them  concentrates  rays  in  a  hori- 
zontal plane,  and  consequently  produces  a  flash.  During  the 
rotation,  if  all  these  lenses  are  equal,  the  navigator  will  see  a 
series  of  equal  white  flashes  succeeding  each  other  ;  a  simple 
scintillating  light  will  be  produced.  If  the  vertical  lenses  are 
alternately  red  and  white,  red  and  white  flashes  will  follow 
each  other  in  alternation.  So,  in  placing  the  red  lenses  two 
apart,  three  apart,  or  four  apart,  lights  will  be  produced  hav- 
ing two,  three,  or  four  flashes  of  white,  followed  by  one  red 
flash.  It  is  necessary  to  remark  in  this  case  that,  as  red  di- 
minishes the  luminous  intensity,  it  is  always  necessary  to 
give  the  red  lens  larger  dimensions  to  compensate  for  this 
loss.  Thus,  by  the  form  given  to  the  lenses,  the  white  and 
red  flashes  may  be  made  equidistant  in  point  of  time,  or  else 
so  that  there  may  be,  between  the  red  flash  and  the  next 
group  of  white  flashes,  a  greater  interval  than  that  which 
separates  these  last  from  each  other.  But  the  red  flashes 
cause  a  loss  of  light  the  greater  as  the  number  of  white  flashes 
is  less.  Thus,  M.  Allard  prefers  in  many  cases  to  separate  the 
groups  of  white  flashes  simply  by  an  interval  of  darkness. 
This  effect  is  produced  by  a  simple  modification  in  the  shape 
of  the  vertical  lenses,  and  the  eight  following  characters  are 
obtained  :  scintillating  lights  with  one,  two,  three,  or  four 
white  flashes  and  one  red  flash ;  wThite  scintillating  light ; 
scintillating  light  in  groups  of  two,  three,  or  four  white 
flashes.  These  characters  are  the  only  ones  permanently 
adopted.  They  possess  the  advantage  of  immediate  and  easy 
recognition  without  the  use  of  any  clock. 

The  regulator  employed  in  light-houses  for  the  electric 
light  is  that  of  M.  Serrin.  It  is  constructed  after  a  special 
model,  worked  out  with  much  care,  and  is  made  of  larger  di- 
mensions than  the  ordinary  model,  and  with  rare  skill.  The 
apparatus  rests  upon  a  metal  table,  supplied  with  rails,  be- 
tween which  are  placed  springs  connected  with  the  two  poles 
of  the  circuit.  It  is  enough  to  push  the  regulator  into  its  place 


FIG.  228.— Electric  light-house  of  Planier,  near  Marseilles. 


380  APPLICATIONS  OF  THE  ELECTRIC  LIGHT. 

for  its  pressure  upon  these  springs  brings  it  into  circuit,  when 
the  arc  immediately  forms.  In  the  first  light-houses,  that 
only  light  a  part  of  the  horizon,  a  system  of  double  rails 
crossing  at  an  acute  angle  makes  the  rapid  change  of  appa- 
ratus easy  by  allowing  the  extinguished  one  to  be  drawn  out 
and  the  other  to  be  pushed  into  its  place. 

In  the  new  apparatus,  such  as  that  of  Planier,  which  lights 
the  whole  horizon,  it  would  have  been  necessary  to  have 
opened  in  the  drums  of  lenses  too  large  an  entrance,  and  other 
arrangements  had  to  be  adopted.  Perpendicular  to  the  rail 
which  enters  the  apparatus,  and  outside,  is  placed  a  second 
rail ;  at  the  point  where  they  meet  is  a  turn-table  similar 
to  those  used  on  railways.  The  manoeuvre  is  quite  as  easy 
and  as  rapid  as  with  the  other  system,  though  the  rotating 
drum  has  to  be  stopped,  and  two  doors  have  to  be  opened. 

A  small  lens  projects  the  magnified  image  of  the  voltaic 
arc  either  on  the  wall  of  the  machinery-room,  as  at  La  Heve, 
or  down  upon  the  working-table,  by  means  of  a  rectangular 
prism,  whose  faces,  forming  the  sides  of  a  right  angle,  have 
received  the  necessary  curvature.  The  keeper  can  then,  with- 
out fatigue,  observe  the  slightest  variations  in  the  position  of 
the  carbons  by  means  of  a  curve  traced  in  advance  and  corre- 
sponding to  the  exact  location  of  the  light ;  he  regulates  or 
adjusts  them  by  means  of  a  regulating-button  with  which  the 
regulator  is  supplied,  and  which  permits  both  carbon-holders 
to  be  raised  or  lowered  without  affecting  the  light. 

The  Alliance  machines  were  the  first  employed.  To-day 
those  used  are  the  magneto-electric  machines  of  M.  de  Meri- 
tens,  which  we  have  already  described.  They  are  placed  along 
with  the  steam-engine  and  shafting  in  a  building  near  the 
light-house,  and  connected  by  perfectly  insulated  wire  with 
the  working-table.  All  the  machines  are  in  duplicate,  which 
insures  the  certainty  of  service  in  case  of  accident  to  one  of 
the  machines,  and,  if  necessary,  on  the  occasions  of  severe 
storms,  makes  it  possible  to  run  both  at  once,  so  as  to  double 
the  intensity  of  the  light. 

Experiments  made  with  a  Gramme  machine,  large  size, 
prove  that  it  can  also  give  excellent  results  as  far  as  its  in- 
tensity and  expense  of  running  are  concerned  ;  but  the  French 
Government  prefers  alternating  currents,  from  considerations 
affecting  the  division  of  the  light  and  the  consumption  of  the 
carbons. 


ELECTRICITY 


LIGHT-HOUSES. 


381 


In  England,  after  first  employing  Holmes's  machines  (Al- 
liance system),  Siemens's  dynamo-electric  machines,  driven 
by  Brown's  hot-air  engines,  are  to-day  used,  as  well  as  the 
magneto-electric  machines  of  M.  de  Meritens. 


FIG.  229.— Arrangement  of  the  Planier  electric  light-house. 

To  better  illustrate  the  arrangements  we  are  describing, 
we  give  here  a  plate  illustrating  the  light-house  recently 
erected  on  Planier  Island,  at  the  entrance  to  the  port  of  Mar- 
seilles (Fig.  228).  It  is  a  cylindrical  tower  of  masonry,  13 '50 


382 


APPLICATIONS   OF  THE  ELECTRIC  LIGHT. 


metres  in  diameter  at  the  level  of  the  foundation,  and  6 -70 
metres  in  diameter  at  the  top  of  the  shaft ;  the  center  opening 
forming  the  stair- well  is  a  cylinder  four  metres  in  diameter. 
The  lantern  is  placed  57*60  metres  above  the  foundation-level, 

and  61*93  metres  above 
high-water  mark.  It  is 
composed  of  a  scintillat- 
ing electric  light,  with 
eclipses  every  five  sec- 
onds, a  red  flash  follow- 
ing three  white  flashes ; 
the  range  should  be  about 
twenty-three  geographical 
miles  (over  twenty-five  and 
a  half  statute  miles).  It 
is  the  same  apparatus  that 
worked  at  the  Champs  de 
Mars  during  the  whole 
time  of  the  Universal  Ex-- 
position of  1878 ;  a  simi- 
lar apparatus  worked  also 
at  the  Palais  de  1'Indus- 
trie  during  the  Electrical 
Exhibition. 

Fig.  229  represents  the 
section  of  the  upper  floors 
and  of  the  lantern.  The 
iron  floor  of  this  lantern- 
room  is  supported  in  its 
center  by  a  hollow  cast- 
iron  column,  through  the 
center  of  which  the  cord 
descends  that  carries  the 
weight  which  moves  the 
outer  drum  of  the  optical 

FIG.  230.-Section  of  the  upper  story  and  lantern       apparatus.        TMs    COrd    is 

of  the  pianier  light-house.  conducted  around  pulleys 

to  a  recess  formed  in  the 

masonry.  The  bars  between  which  the  glasses  of  the  lantern 
are  fastened  have  inclined  faces,  so  that  they  do  not  dimin- 
ish the  light  sensibly  in  any  direction. 

The  optical  apparatus  is  shown  in  Fig.  230  ;  it  is  composed 


ELECTRICITY  IN  LIGHT-HOUSES.  383 

of  a  stationary  lantern  of  *60  metre  interior  diameter,  and  of 
a  movable  outer  drum,  formed  of  vertical  lenses.  In  spite  of 
the  bad  economy  of  passing  the  light  through  two  lenses  suc- 
cessively, this  combination  has  been  adopted  because  by  it 
the  necessary  duration  can  be  given  to  the  flashes  by  increas- 
ing the  horizontal  divergence  of  the  lenses  of  the  drum 
without  modifying  the  vertical  divergence  due  to  the  fixed 
lantern  lenses. 

The  vertical  drum  is  composed  of  six  groups  of  four  lenses, 
one  red  and  three  white.  The  lenses  designed  to  produce  red 
flashes  include  an  angle  three  times  greater  than  that  of  the 
lenses  giving  white  flashes  ;  this  relation  is  necessary  to  insure 
the  same  range  to  it  as  to  the  others.  It  turns  upon  a  circle  of 
rollers  by  means  of  mechanism  placed  in  the  base  ;  the  regu- 
larity of  movement  is  insured  by  a  fan-regulator  of  Foucault. 

Apparatus  of  this  kind  gives  an  intensity  about  fifty  times 
greater  than  that  of  the  electric  light  within  it  ;  the  white 
vertical  lenses  nearly  quadruple  this  intensity,  so  that  the 
flashes  are  200  times  greater  than  the  original  light.  If  this 
latter  be  supposed  equal  to  500  carcels,  each  white  flash  will 
be  equal  to  about  100,000  carcels.  The  lenses  producing  the 
red  flash  give  three  times  this  intensity,  to  compensate  the 
diminution  due  to  the  coloration. 

The  adoption  of  the  electric  light  in  light-houses  presents 
the  following  advantages  :  It  makes  possible  the  increasing  at 
will  of  the  luminous  intensity,  and,  in  consequence,  the  range 
of  the  light  in  stormy  weather  ;  the  importance  of  this  will  be 
understood  when  it  is  stated  that  the  unit  light  visible  at  a 
distance  of  nearly  nine  kilometres  in  clear  weather,  or  seven 
in  average  weather,  can  not  be  discerned  more  than  about  five 
in  stormy  weather  ;  beyond  this  comes  foggy  weather,  when 
almost  or  quite  nothing  is  discernible.  Careful  observations 
have  proved  the  existence  of  the  following  differences  per  100 
observations  : 

At  a  distance  of  more  than  37  kilometres,  Ue       *"<*' 


than  27  Metres...  ^       JJ 


This  superiority  at  long  ranges  is  due  to  the  fact  that  the 
temperature  of  the  arc  is  much  higher,  and  its  specific  inten- 

26 


384  APPLICATIONS   OF  THE  ELECTRIC  LIGHT. 

sity  much  more  considerable.  Thus  the  intensity  per  square 
centimetre  of  an  electric  light  of  200  carcels  is  550  times  greater 
than  that  of  the  same  surface  of  a  mineral-oil  lamp  with  five 
wicks.  If  now  it  be  compared  with  the  sunlight,  it  will  be 
found,  according  to  M.  Allard,  that  the  intensity  of  this  latter 
light  upon  the  earth  is  equal  to  a  light  of  6,000  carcels  at  a 
distance  of  one  metre,  and,  taking  into  account  the  thickness 
of  the  atmosphere,  estimated  at  nine  kilometres,  the  luminous 
intensity  of  the  solar  surface  per  square  centimetre  is  equal 
to  12,000  carcels,  or  47  times  as  powerful  as  the  electric  light, 
and  more  than  2,600  times  that  of  an  oil  lamp  with  five  wicks. 

The  electric  light  also  makes  it  possible,  as  we  have  seen, 
to  prolong  the  duration  of  the  flashes  in  rotating  lanterns  by 
the  use  of  vertical  lenses,  which  move  in  front  of  the  fixed 
lantern,  giving  them  six  times  their  normal  power. 

It  also  makes  it  possible,  on  account  of  the  lightness  of 
the  apparatus,  to  suppress,  in  the  list  of  characteristic  differ- 
ences, the  use  of  a  stated  period  or  duration  in  minutes  and 
seconds.  With  the  new  characters  which  can  be  employed 
on  account  of  it,  every  light-house  declares  its  name  more 
quickly  and  certainly,  without  the  necessity  of  consulting  a 
watch. 

This  same  increase  of  power  of  the  lights  makes  it  practi- 
cable to  add  to  the  characters  the  use  of  red  lights,  in  spite 
of  the  loss  resulting  from  the  coloration,  the  red  light  having 
only  one  quarter  the  range  of  white  light;  for  green  light  it 
is  still  worse,  only  one  eighth  ;  thus  this  last  can  only  be  em- 
ployed for  stationary  range-lights  and  for  signals  at  sea. 

Finally,  the  intensity  of  the  electric  light  being  much 
greater  than  is  necessary  for  an  ordinary  mainland  light- 
house, MM.  Sautter  and  Lemonnier  have  profited  by  it  to 
cause  it  to  produce  a  luminous  plume,  thrown  vertically  up 
from  the  light-house  ;  thanks  to  its  height,  this  plume  can  be 
seen  from  ninety  to  one  hundred  kilometres,  where  the  ordi- 
nary geographical  range,  limited  by  the  curvature  of  the 
earth,  rarely  exceeds  fifty-five  kilometres.  This  will  permit 
navigators  to  direct  their  course  farther  from  the  coast-line, 
and  this  is  sometimes  a  condition  of  considerable  importance. 
It  is  thus  that  in  the  Sea  of  Azof  most  vessels  that  enter  this 
sea  by  the  Straits  of  Yenikale  to  load  with  corn  at  Taganrog  or 
at  Berdiansk,  wish  naturally  to  follow  the  straightest  possible 
line,  traversing  the  sea  where  it  is  widest  and  far  out  of  range 


ELECTRICITY  IN  LIGHT-HOUSES. 


385 


of  the  light-houses  on  the  coast.     A  luminous  indication  of 
the  position  of  Berdiansk,  as  they  enter  the  Sea  of  Azof, 


FIG.  231. — Fixed  light  electric  light-house. 

would  be  most  valuable  to  them,  and  to  furnish  such  indica- 
tion the  Kussian  Government  have  engaged  MM.  Sautter  and 


386  APPLICATIONS   OF  THE  ELECTRIC  LIGHT. 

Lemonnier  to  construct  an  electric  light-house,  surmounted  by 
a  vertical  luminous  plume,  which  will  be  visible  at  Yenikale. 

The  apparatus  is  that  of  a  light  flashing  every  five  seconds, 
with  eclipses  three  seconds  in  duration.  The  optic  system 
consists  of  a  fixed  lantern  one  metre  in  diameter,  in  which  the 
upper  catadioptric  part  is  replaced  by  a  projection  lens  whose 
optical  axis  is  vertical,  and  passes  through  the  voltaic  arc  of 
the  apparatus ;  it  is  this  projector  which  produces  the  per- 
manent beam  or  luminous  plume. 

Following  out  this  principle,  the  same  engineers  have  con- 
structed a  model  of  an  electric  light-house,  shown  in  Fig.  231. 
It  is  supplied,  like  the  preceding,  with  a  projection  lens,  and 
the  lower  part  has  been  enlarged  so  as  to  utilize  the  most 
intense  rays  of  the  voltaic  arc  produced  by  continuous- current 
machines. 

A  Gramme  regulator  is  employed ;  it  is  supported  from 
above,  which  does  away  with  the  tables  and  the  supports ; 
moreover,  the  lamp  is  double,  and  can  burn  all  night  without 
needing  replacement.  It  is  enough  to  turn  the  lamp  through  an 
arc  of  180°  around  its  pivot  for  a  second  pair  of  carbons  to  be- 
come lighted  in  the  focus  of  the  optical  apparatus  ;  the  period 
of  extinction  is  inappreciable. 

The  factory  of  MM.  Sautter  and  Lemonnier,  founded  in  1825 
under  the  direction  of  Augustin  Fresnel,  is  one  of  the  first  in 
which  the  electric  light  was  applied  to  the  illumination  of 
workshops.  Fig.  232  illustrates  this  installation,  of  which  we 
shall  speak  further  on. 

The  latest  improvements  shown  in  the  Electrical  Exhibi- 
tion of  1881,  in  the  production  and  distribution  of  currents, 
gives  room  to  hope  that  light-houses,  even  when  far  from  the 
coast,  and  in  situations  which  do  not  permit  the  use  of  ma- 
chines, may  profit  by  it,  as  we  have  seen  that  at  the  present 
day  these  latter  can  be  placed  at  a  considerable  distance  from 
the  lamp.  Perhaps  the  time  will  come  when  the  most  impor- 
tant buoys  can  be  lighted  at  night,  either  directly  or  by  pro- 
jection. 


OF  THE  ELECTRIC  LIGHT. 


CHAPTER  II. 

THE  ELECTEIC  LIGHT  IN  WAR  AND  NAVIGATION. 

NIGHT  does  not  put  a  stop  to  military  operations,  it  only 
imposes  different  conditions,  which  the  electric  light  can 
modify  in  more  than  one  way  by  the  intensity  of  the  light 
which  it  produces.  It  can  especially  serve  to  direct  night 
attacks,  and  at  the  same  time  render  visible  the  outworks  of  a 
place  or  surroundings  of  a  vessel  threatened  with  a  secret 
attack.  At  sea  it  can  also  furnish  a  sort  of  light-house  car- 
ried by  each  vessel,  to  signal  its  approach  to  others  and  pre- 
vent collisions.  Finally,  without  speaking  for  the  moment  of 
a  number  of  other  uses,  it  gives  very  powerful  luminous  sig- 
nals, which  have  originated  a  system  of  optical  telegraphy 
even  more  useful  for  military  correspondence  in  the  enemy's 
country  than  for  communications  between  vessels,  as  it  re- 
quires no  intermediary  wire. 

I.   MILITARY  AND  MARITIME  APPLICATIONS  FROM  1855 

TO  1877. 

The  importance  of  this  new  element  of  action  was  appre- 
ciated at  an  early  date  by  studious  officers,  perhaps  even  at 
an  epoch  when  no  practical  means  were  known  of  employing 
it  efficaciously.  The  French  fleet  tried  it  in  1855  at  the  siege 
of  Kinburn,  during  the  campaign  of  the  Baltic.  A  parabolic 
reflector  was  used  to  project  a  beam  of  electric  light  upon  the 
point  attacked.  A  short  time  after,  M.  Martin  de  Brettes 
published  an  extensive  work  in  which  he  enumerated  all  the 
services  that  the  electric  light  could  render  to  the  art  of  war, 
either  for  the  lighting  up  of  siege- works  and  military  opera- 
tions, or  as  a  means  of  telegraphic  communication. 

The  war  in  Italy,  in  1859,  directed  the  attention  of  the 
French  military  authorities  to  this  subject,  who  instituted 
experiments  to  fix  the  elements  of  construction  of  an  appa- 
ratus fit  for  campaign  use.  These  experiments,  conducted  at 
Paris,  were  performed  with  a  Grenet  battery  and  a  parabolic 
reflector  like  that  which  had  been  used  before  Kinburn.  But 
the  peace  of  Yillaf ranca  interrupted  them  before  long,  and  the 
Italians  next  took  them  up.  In  the  short  campaign  of  1861, 


THE  ELECTRIC  LIGHT  IN  WAR  AND  NAVIGATION.        389 

against  the  King  of  Naples,  General  Menabrea  used  a  light- 
ing apparatus  constructed  upon  similar  principles,  and  capa- 
ble of  giving  useful  results  at  a  distance  of  1,500  metres. 
This  much  at  least  was  indicated  by  the  test  experiments,  for 
the  apparatus,  prepared  for  the  attack  of  Gaeta,  had  no 
chance  to  be  tried  in  actual  practice — that  is  to  say,  before 
the  enemy,  in  the  midst  of  siege  operations. 

The  military  use  of  the  electric  light  met  a  greater  obstacle 
in  field  use  than  elsewhere,  due  to  the  inconvenience  of  the 
means  of  production.  Batteries  were  still  the  only  available 
source,  and,  to  obtain  an  intense  light,  very  many  cells  were 
required.  These  were  not  only  cumbrous  and  fragile  for 
transportation,  but  they  were  difficult  and  slow  to  set  to 
work,  which  deprived  them  of  much  of  their  practical  value 
in  a  condition  of  things  where  promptitude  is  the  first  ele- 
ment of  success. 

Toward  1862  the  Alliance  magneto-electric  machine,  con- 
siderably improved,  furnished  a  source  of  electricity  less  com- 
plicated and  more  powerful.  But  it  still  was  too  heavy,  so 
that  its  transportation  for  an  army  in  the  field  was  almost 
impossible.  The  same  obstacle  did  not  exist  in.  the  case  of 
ships,  which  placed  it  in  position  as  a  part  of  their  equip- 
ment. Thus  the  Alliance  machine  was  first  used  on  the  sea. 
Its  first  application  is  due  principally  to  the  initiative  of  M. 
Georgette  Dubuisson,  commandant  of  the  yacht  of  Prince 
Napoleon,  the  Reine  Hortense.  In  1867  this  yacht  was  pro- 
vided with  an  electric  beacon,  with  regulator,  which  lighted 
the  pathway  in  advance  of  it,  and  enabled  it  to  enter  at  night 
into  several  Mediterranean  ports  of  most  dangerous  approach 
with  as  much  ease  as  if  it  had  been  full  day. 

This  minor  triumph  of  electricity  inevitably  attracted  at- 
tention. M.  Eugene  Pereire,  engineer  of  the  Compagnie  Trans- 
atlantique,  immediately  introduced  similar  apparatus  on  the 
Sainte-Laurent,  then  on  other  ships  of  the  same  company, 
where  it  was  fully  appreciated.  Soon  after  the  Parfait,  the 
d'Estrees,  the  Coligny,  the  Heroine,  and  finally  the  France, 
were  supplied  also  with  an  electric  light  maintained  by  an 
Alliance  machine. 

In  1870  the  Emperor's  new  yacht,  Hirondelle,  received  in 
its  turn  a  similar  plant,  which  thereupon,  as  a  matter  of 
course,  chose  the  entrance  into  Cherbourg  for  its  trial  trip, 
where  the  ship  broke  its  cutwater  and  demolished  its  stem  to 


390  APPLICATIONS   OF  THE  ELECTRIC   LIGHT. 

a  considerable  extent  against  the  Grande  Douane  wharf.  More 
important  events  prevented  the  perfecting  of  this  defective 
installation.  But,  during  the  same  year,  electricity  made  a 
greater  success  upon  another  imperial  yacht,  the  Greif,  be- 
longing to  the  Emperor  of  Austria.  This  yacht  entered  Vil- 
lafranca  and  several  ports  of  the  Mediterranean  by  night,  as 
the  Reine  Hortense  had  already  done,  and  by  night  went 
through  the  Suez  Canal,  lighting  marvelously  the  shores.  In 
1871  the  Russian  navy  also  introduced  upon  several  ships 
electric  lights  with  lenticular  projectors,  which  gave  them  the 
power  of  passing  by  night  the  narrow  straits  of  the  Baltic, 
of  entering  the  port  of  St.  Petersburg,  and  of  performing  for- 
tunate rescues. 

What  was  then  sought  in  the  electric  light  was  a  means  of 
perceiving  the  obstacles  which  could  menace  the  ship  on  her 
course.  It  played  the  role  of  lantern  that  every  peasant  car- 
ries with  him  at  night  to  keep  him  in  the  streets  of  the  village 
when  there  is  no  moon.  The  same  necessity  becomes  more 
pronounced  when  a  narrow  river  is  to  be  navigated  at  night. 

In  this  connection  we  must  not  pass  over  the  part  taken 
by  M.  Menjer  (Fig.  233).  By  an  electric  light  operated  by  a 
Gramme  machine,  driven  by  a  Brotherhood  engine,  his  yacht 
easily  passed  at  night  through  the  windings  of  the  Marne 
and  the  Seine,  between  Paris  and  his  large  chocolate  factory 
at  Noisiel. 

This,  it  is  true,  is  an  exceptional  case,  and  if  such  lights 
should  be  employed  to  facilitate  the  course  of  vessels  in  the 
darkness,  the  dazzling  produced  by  them  might  render  them 
more  annoying  than  useful.  It  would  be  necessary  to  find  a 
means  of  utilizing  this  light  while  avoiding  the  trouble.  It 
would  be  doubtless  more  practicable  to  light  up  difficult  pas- 
sages as  a  boulevard  is  lighted  up  for  the  travel  of  vehicles. 

On  land,  the  weight  of  the  Alliance  machine  made  its  use 
in  really  active  military  operations  difficult.  But  this  did  not 
destroy  all  hopes  of  utilizing  the  electric  light  in  war.  The 
Universal  Exposition  of  1867  had  already  proved  this.  The 
Austrian  Government  sent  to  it  large  parabolic  mirrors,  in 
silvered  metal,  designed  to  project  the  light  of  an  electric 
lamp  placed  in  the  focus  of  the  parabola.  A  number  of  de- 
signs showed  the  military  applications  that  were  contem- 
plated. In  1869  Russia  had  similar  plans  in  contemplation, 
whose  existence  is  only  known  to  us  by  the  purchase  of  a 


. 

1. 


392  APPLICATIONS  OF  THE  ELECTRIC  LIGHT. 

certain  number  of  Alliance  machines,  and  of  lenticular  pro- 
jectors. It  is  entirely  probable  that  other  powers  did  the 
same  in  secret. 

A  short  while  after,  the  Franco- German  War  of  1870-71 
gave  the  electric  light  a  chance  to  make  its  debut  upon  the 
field  of  battle,  under  precisely  those  circumstances  where  its 
use  was  best  understood — in  a  great  siege. 

The  defenders  of  Paris  used  it  both  as  a  source  of  light 
and  as  a  means  of  telegraphic  communication  by  optical  sig- 
nals. The  lamps  were  those  of  Foucault  and  Serrin ;  the 
source  of  electricity  was  Bunsen  batteries,  of  not  more  than 
fifty  elements,  placed  in  the  posies  d'octroi  all  around  the 
city.  Upon  one  point,  nevertheless,  near  Montmartre,  an  Al- 
liance machine  had  been  placed,  which  naturally  furnished  a 
much  more  energetic  current  and  consequently  a  more  in- 
tense light.  The  forts  had  also  electric  lamps,  supplied  from 
Bunsen  batteries.  But  the  reflectors  which  were  used  to 
direct  the  luminous  beam  were  quite  insufficient,  and  the 
lights  themselves  were  not  sufficiently  powerful  to  light  all 
expected  localities. 

The  electric  light,  nevertheless,  rendered  considerable  ser- 
vice ;  it  prevented  several  nocturnal  surprises,  and  revealed 
several  movements  of  the  enemy  which  would,  without  it, 
have  escaped  notice.  The  Montmartre  light,  supplied  by  the 
magneto-electric  machine,  bathed  with  its  rays  the  plateau  of 
Argenteuil. 

The  Germans  used  the  electric  light  very  skillfully  to  direct 
their  battery  practice  and  keep  track  of  our  night  operations. 
They  had  machines  at  their  disposal,  and  hence  obtained 
much  more  powerful  lights  than  were  given  by  our  lamps  sup- 
plied from  Bunsen  batteries. 

The  dynamo-electric  machine  of  M.  Gramme,  invented  and 
presented  to  the  Academy  of  Sciences  at  Paris  in  1870,  could 
only  be  known  industrially  after  the  Franco-German  war. 
More  powerful  and  much  lighter  than  the  Alliance  machine, 
it  was  a  source  of  electricity  much  better  adapted  to  the  ne- 
cessities of  war.  Soon  after,  the  first  Siemens  machine  ap- 
peared in  Germany,  which  presented  analogous  advantages. 
The  attention  of  military  engineers  was  then  again  directed 
to  the  electric  light.  The  Germans  first  studied  it.  At  the 
Universal  Exposition  of  Vienna  in  1873,  they  sent  large  pro- 
jection apparatus,  with  an  electric  lamp,  supplied  by  the  first 


THE  ELECTEIC  LIGHT  IN  WAK   AND  NAVIGATION.        393 

Siemens  machine,  designed  by  M.  Heffner  von  Alteneck.  In 
the  French  section  a  new  electric  projector  was  to  be  seen, 
specially  destined  for  use  at  sea ;  but  it  belonged  to  the  do- 
main of  individual  industry  ;  it  was  the  work  of  MM.  Sautter 
and  Lemonnier,  the  great  light-house  builders  of  Paris. 

The  Russian  navy  was  the  first  to  substitute  the  Gramme 
for  the  Alliance  machines.  In  1873  and  1874,  the  Peter  the 
Great  and  the  Livadia  tried  the  new  apparatus,  with  lenticu- 
lar projectors  analogous  to  those  of  light-houses.  This  appa- 
ratus, constructed  by  MM.  Sautter  and  Lemonnier,  gave  a  light 
of  about  five  hundred  carcels,  and  showed  edifices  in  the  dark- 
est of  nights  three  kilometres  distant.  It  will  be  seen  how 
great  was  the  progress  since  1870.  The  Livadia  in  particular 
found  it  useful  on  more  than  one  occasion,  and  was  able  to  fol- 
low at  night  a  buoyed  channel  not  over  twenty  metres  wide. 

In  France  it  is  the  commercial  marine  that  leads  the  way 
for  the  national  marine  to  follow.  We  have  seen  that  in  1867 
M.  Eugene  Pereire  had  placed  upon  one  of  the  large  transat- 
lantic steamers,  the  Sainte-Laurent,  electric  projectors  sup- 
plied by  Alliance  machines.  After  first  having  attracted 
numerous  imitators,  these  attempts  were  gradually  abandoned 
in  face  of  the  passive  resistance  of  old  habits.  Most  captains 
saw  in  the  new  apparatus  only  a  cumbrous  luxury,  expensive, 
awkward  in  use,  and  of  doubtful  efficacy.  The  projectors 
had  sought  in  it  an  argument  for  reducing  the  rates  of  insur- 
ance against  the  accidents  of  the  sea,  because  the  chances  of 
collision  were  lessened.  Naturally,  the  insurance  companies 
did  not  care  to  yield  too  quickly,  and  the  projectors,  deceived 
in  their  hopes,  soon  ceased  to  impose  upon  the  captains  a 
costly  encumbrance  that  was  attended  by  no  compensation. 

The  discovery  of  the  Gramme  machine  diminished,  how- 
ever, the  force  of  these  objections,  as  it  placed  at  the  disposal 
of  the  marine  less  cumbrous,  much  more  powerful,  and  at  the 
same  time  cheaper,  machines.  M.  Eugene  Pereire  again  ad- 
dressed himself  to  the  question,  and,  in  1876,  he  ordered  M. 
Fontaine  to  establish  the  electric  light  upon  the  transatlantic 
steamer  Amerique. 

The  following  year,  in  1877,  the  navy  took  up  the  long  in- 
terrupted experiments.  MM.  Sautter  and  Lemonnier  placed 
upon  the  Richelieu  and  the  Suffren  electric  lights  with  len- 
ticular projectors  like  those  which  had  been  constructed  four 
years  before  for  the  Russian  navy.  During  this  period  the 


394:  APPLICATIONS  OF  THE  ELECTRIC  LIGHT. 

army  had  been  occupied  also  with  this  investigation,  and  at 
the  commencement  of  this  same  year  (1877)  M.  Mangin,  colo- 
nel of  engineers,  combined  a  new  projector  with  a  mirror  of 
a  particular  form,  to  which  we  should  give  a  moment's  at- 
tention, because  it  is  the  only  one  adopted  to-day  in  this 
country  (France)  for  military  or  maritime  operations.  Ger- 
many has  retained  parabolic- mirror  projectors,  and  lenticu- 
lar projectors.  As  for  the  commercial  marine,  the  latter  are 
the  ones  generally  in  use. 

II.   ELECTEIC  PEOJECTOES  OF  THE  FEENCH  AEMY. 

The  principal  defect  of  lenticular  projectors  was  that  they 
occasioned  a  considerable  loss  of  light.  Though  wasting  less 
light,  the  parabolic-mirror  projectors  presented  serious  diffi- 
culties of  construction,  and  were  easily  bent  out  of  shape. 
The  aplanatic-mirror  projector  of  Colonel  Mangin,  invented 
in  the  beginning  of  1877,  was  designed  specially  to  avoid  this 
double  inconvenience. 

Spherical-surface  mirrors  are  much  easier  to  construct  and 
keep  intact  than  parabolic  mirrors  ;  but  they  do  not  bring  all 
the  luminous  rays  into  parallelism,  so  that  there  is  a  considera- 
ble lateral  dispersion  of  light  in  long-distance  projections. 
M.  Mangin  formed  his  mirror  by  superimposing  two  spherical 
surfaces  of  different  curvature.  These  two  surfaces  are  rep- 
resented in  their  relation  to  each  other  by  the  two  faces  of  a 
concavo-convex  lens,  whose  second  face — the  convex  face — is 
silvered,  and  forms  the  back  of  the  mirror — that  is  to  say,  the 
reflecting  surface.  The  luminous  rays  which  fall  upon  the 
mirror  and  are  reflected  from  the  silvered  face,  twice  traverse 
the  glass,  and  are  twice  refracted  in  opposite  directions.  The 
final  result  of  these  changes  of  direction  depends  upon  the 
ratio  of  the  lengths  of  the  radii  of  the  two  spherical  surfaces. 
By  combining  them  in  a  suitable  manner,  Colonel  Mangin  has 
completely  abolished  what  physicists  call  spherical  aberra- 
tion, and  has  succeeded  in  bringing  all  the  rays  into  the  most 
absolute  parallelism. 

The  projector  has  the  form  of  a  cylindrical  box,  quite 
short,  of  a  diameter  of  ninety  centimetres,  whose  back  is 
formed  by  the  aplanetic  mirror  we  are  describing,  a  certain 
distance  in  front  of  which  the  voltaic  arc  is  placed.  It  is  an 
arc  playing  between  two  carbons  that  are  brought  together  by 


THE  ELECTRIC  LIGHT  IN  WAR   AND  NAVIGATION.        395 

hand,  by  means  of  a  thumb-screw  worked  from  the  outside. 
There  is  therefore  no  regulator.  This  rudimentary  arrange- 
ment, which  would  be  inadmissible  in  any  other  case,  suits 
perfectly  cases  of  lighting  of  short  duration,  and  which  need 
no  particular  steadiness.  The  carbons,  instead  of  being  ver- 
tical, are  inclined  at  an  angle  of  about  thirty  degrees ;  the 


FIG.  234. — Mangin  projector. 

experiments  of  MM.  Sautter  and  Lemonnier,  of  which  we  have 
spoken  in  Chapter  IV  (Fig.  23),  have  shown  that  they  thus 
give  a  greater  quantity  of  useful  light,  on  account  of  the  po- 
sition which  the  cup  or  crater  of  the  positive  carbon  then 
occupies.  Finally,  an  auxiliary  lens,  placed  between  the  arc 
and  the  mirror,  collects  and  projects  upon  it  a  part  of  the 


396  APPLICATIONS  OF  THE  ELECTRIC   LIGHT. 

light  which  would  otherwise  escape  its  action,  and  thus  in- 
creases the  intensity  of  the  lighting ;  it  makes  possible,  in 
fact,  the  utilization  of  all  the  rays  emitted  in  an  angle  of  one 
hundred  degrees,  while  the  mirror  by  itself  would  only  util- 
ize them  within  an  angle  of  sixty-eight  degrees  (Fig.  234). 

When  the  electric  light  is  placed  in  the  focus  of  the  mir- 
ror, the  projector  throws  out  a  very  powerful  cylindrical  lu- 
minous beam,  twenty  times  more  powerful  than  with  an  ordi- 
nary spherical  mirror,  but  whose  area  of  lighting  is  very 
limited.  To  rapidly  reconnoitre  a  suspected  ground,  it  is 
necessary  to  enlarge  this  field  of  view  by  abandoning  the 
cylindrical  beam,  and  by  giving  it  a  slightly  conical  form. 
This  result  is  obtained  in  the  most  simple  manner,  by  remov- 
ing the  luminous  center  from  the  focus  of  the  mirror  and 
placing  it  nearer  to,  or  further  from,  this  focus.  The  change 
is  quickly  effected  by  a  screw  placed  on  the  exterior.  When 
the  voltaic  arc  is  displaced  four  centimetres,  the  surface 
lighted  at  one  kilometre  distance  increases  from  fifteen  square 
metres  to  one  hundred  and  fifteen,  and  at  four  kilometres  dis- 
tance the  surface  lighted  increases  to  four  hundred  and  sixty 
square  metres. 

The  divergence  thus  obtained  is  produced  in  the  direction 
of  height,  as  well  as  in  that  of  width.  As  it  is  the  earth  only 
—that  is  to  say,  the  horizon — which  is  usually  to  be  inspected, 
the  light  cast  up  in  the  sky  is  lost  without  benefit.  To  avoid 
this  trouble,  a  disk  of  glass  is  placed  in  front  of  the  pro- 
jector, which  disk  is  formed  of  a  series  of  divergent  piano- 
cylindrical  lenses,  which  spread  out  horizontally  the  luminous 
beam  in  such  a  manner  as  to  give  the  field  of  illumination  a 
nearly  rectangular  form ;  the  effect  is  the  same  as  if  the  lu- 
minous cone  had  been  flattened  against  the  earth,  as  a  paper 
cornet  might  be.  By  this  process  divergences  of  twelve  to 
fifteen  degrees  can  be  attained  with  a  beam  that  originally 
had  only  two  degrees  divergence  on  leaving  the  mirror. 

The  projector  is  carried  upon  a  small  carriage  (Fig.  235) 
that  one  horse  can  easily  draw  about  where  it  is  to  be  used,  as 
its  total  weight  is  not  over  seven  hundred  and  fifty  kilo- 
grammes. The  apparatus  is  mounted  upon  trunnions,  and 
suspended  so  that  it  can  easily  be  turned  in  all  directions,  and 
be  made  to  sweep  the  ground  as  easily  as  the  eye  itself. 

It  is  true  that  this  electric  eye  has  to  be  animated  by  a 
dynamo -electric  machine,  driven  itself  by  a  steam-engine 


THE  ELECTRIC   LIGHT   IN  WAR  AND  NAVIGATION.        397 

which  draws  its  supply  from  a  boiler.  These  three  parts  form 
a  plant  that  must  be  movable  so  as  to  follow  the  projector, 
and  they  weigh  nearly  five  thousand  kilogrammes  with  the 
wagon  carrying  them. 


FIG.  235. — Mangin  projector,  with  its  accessories,  mounted  upon  the  field-wagon. 

MM.  Sautter  and  Lemonnier,  who  construct  all  these  appa- 
ratus, have  combined  them  so  as  to  diminish  their  weight 
without  reducing  their  power.  The  machine  is  a  Gramme 


398  APPLICATIONS   OF  THE  ELECTRIC  LIGHT. 

machine  of  the  D.  Q.  type,  which  gives  a  light  of  4,000  carcels 
—almost  the  most  powerful  that  can  be  produced  under  good 
conditions.  It  is  driven  directly  by  a  Brotherhood  engine, 
which  has  been  chosen  simply  on  account  of  its  small  volume, 
and  because  it  is  adapted  to  drive  the  dynamo-electric  machine 
directly  without  the  intervention  of  pulleys  and  belts,  whose 
working  is  interfered  with  by  the  least  rain.  Finally,  the 
field  boiler  has  the  advantage  of  rapidly  getting  up  steam,  and 
of  furnishing  steam,  as  it  were,  as  soon  as  the  fire  is  started. 

Thus  arranged,  the  Mangin  projector  has  a  useful  range  of 
five  or  six  kilometres.  The  numerous  experiments  to  which 
it  has  been  subjected  since  1878,  at  the  fortress  of  Mount  Ya- 
lerien,  show  even  a  better  result,  because  in  full  night  all  the 
details  of  the  towers  of  the  Trocadero  could  be  seen,  situated 
at  a  distance  of  nearly  eight  kilometres.  At  five  kilometres 
houses,  carriages,  and  the  movements  of  soldiers  could  be 
well  distinguished  ;  at  three  and  a  half  kilometres  it  was  pos- 
sible to  count  the  dispersed  soldiers  and  to  recognize  their 
occupations. 

In  all  these  experiments,  the  observer  being  placed  near 
the  luminous  source,  the  light  had  to  pass  twice  over  the 
given  space  to  return  to  him.  In  its  passage  away  from  the 
observer,  it  weakened  in  proportion  to  the  square  of  the  dis- 
tance, and,  on  its  return,  proportionally  to  the  square  of  the 
square — that  is  to  say,  to  the  fourth  power  of  the  distance. 
For  instance,  when  the  object  to  be  examined  from  a  distance 
is  only  lighted  one  hundredth  as  much  as  if  it  were  near  the 
luminous  focus,  the  observer,  situated  near  this  focus,  will 
only  receive  a  light  of  one  millionth  this  intensity.  That 
which  diminishes  the  visibility  of  objects  is  especially  their 
distance  from  the  observer.  But  in  war  this  distance  can  be 
shortened  by  advancing  the  observers  near  the  enemy,  while 
the  projector  would  remain  behind  under  protection  of  the 
cannon. 

The  large  projectors  of  ninety  centimetres  are  designed 
especially  for  the  defence  of  fortified  places,  and  of  the  coasts. 
They  are  relied  on  in  following  the  movements  and  operations 
of  the  enemy.  Toward  the  middle  of  1881,  MM.  Sautter  and 
Lemonnier  sold  forty  to  the  French  Government,  of  which 
ten  were  in  service  in  fortified  places,  and  thirty  on  the  coasts. 
Each  of  these  apparatus,  with  the  machines  attached  to  them 
and  their  accessories,  cost  nearly  30,000  francs. 


FIG.  236.— Portable  apparatus,  with  Brotherhood  e 


ie  and  Gramme  machine,  for  use  with  Mangin  projector. 


THE  ELECTRIC   LIGHT  IN    WAR  AND   NAVIGATION.        399 

For  field  service  a  somewhat  lighter  model  was  chosen, 
easier  to  transport  but  of  somewhat  less  power.  The  pro- 
jector has  two  thirds  of  the  diameter  of  the  other — only  sixty 
centimetres — and  has  no  auxiliary  lens.  Its  range  does  not 
exceed  four  or  five  kilometres.  It  is  supplied  by  a  weaker 
Gramme  machine,  of  the  C.  Q.  type,  producing  a  light  of  2,500 
carcels  intensity.  The  Brotherhood  engine  and  the  Field 
boiler  are  also  of  smaller  size,  but  the  general  arrangement  is 
the  same. 

The  projector- carriage  can  be  drawn  by  men,  and  be  re- 
moved from  the  engine  and  machinery-carriage,  which  sup- 
plies the  current,  by  paying  out  the  cable  supplied  to  it.  A 
dozen  examples  of  this  type  are  still  in  service,  and  are  a  little 
less  expensive  than  the  others. 

Finally,  there  is  a  third  model,  much  lighter,  but  also 
much  weaker,  as  its  range  hardly  attains  three  kilometres. 
It  is  a  projector  of  forty  centimetres  diameter,  with  a  Gramme 
machine  of  only  1,600  carcels  power.  The  whole  in  this  case 
is  carried  upon  a  single  carriage.  The  projectpr  is  so  light 
that  two  men  can  dismount  it,  carry  it  off  some  distance,  and 
place  it  in  position  on  a  movable  base  instead  of  the  special 
carriage,  in  this  case  dispensed  with.  This  third  model  is 
designed  for  subsidiary  lighting  and  for  the  small  forts  situ- 
ated along  our  new  frontier,  to  arrest  the  movements  of  an 
invading  army.  They  can  also  be  employed  to  project  upon 
the  clouds  luminous  jets,  which  would  serve  as  signals,  and 
would  form  a  sort  of  special  optical  telegraph.  At  the  present 
time  the  French  army  has  only  eight  apparatus  of  this  kind. 

The  Mangin  projectors,  only  four  years  invented,  have 
never  had  a  chance  to  be  tried  on  the  battle-field  or  in  sieges. 
They  were  used,  however,  at  the  beginning  of  the  Tunis  expe- 
dition. The  frigate  Surveillante  used  them  in  exploring  the 
coast  of  the  island  of  Tabarka,  before  disembarking  our  troops 
(Fig.  237),  and  possibly  the  effect  produced  upon  the  natives 
by  this  apparition,  terrifying  to  their  eyes,  had  something  to 
do  in  facilitating  the  operation. 

III.   THE  ELECTRIC  LIGHT  AT  SEA. 

As  we  have  said  before,  it  is  to  M.  Eugene  Pereire  that,  in 
France,  is  due  the  initiative  in  taking  up  again  nautical  light- 
ing in  March,  1876,  after  the  abandonment  of  the  long  trials 

27 


THE  ELECTKIO  LIGHT  IN   WAR  AND  NAVIGATION.        401 

already  gone  through  by  the  Compagnie  Transatlantique, 
under  his  impulse,  when  the  Alliance  machine  was  their  only 
generator.  The  new  system  was  put  into  the  steamer  Amer- 
ique  by  M.  H.  Fontaine,  with  the  assistance  of  the  captain, 
M.  Pouzalz.  We  give  the  description  in  the  words  of  M.  H. 
Fontaine  himself  : 

"The  light  is  placed  at  the  top  of  a  little  tower,  which  is 
ascended  by  interior  steps,  without  the  necessity  of  going  upon 
the  deck,  because  the  tower  comes  over  one  of  the  regular  com- 
panion-ways. This  arrangement  is  very  advantageous,  espe- 
cially in  bad  weather,  when  the  ship's  bows  are  hard  of  access 
by  the  bridge.  The  tower  was  originally  seven  metres  high, 
but  M.  Pouzalz  made  it  two  metres  less,  to  give  it  more  sta- 
bility and  lower  the  level  of  the  beam  of  light,  so  that  now 
this  tower  rises  five  metres  above  the  deck.  Its  diameter  is 
one  metre,  and  it  is  placed  forward  on  the  ship,  about  fifteen 
metres  from  the  bow. 

"The  lantern  (properly  so  called)  is  made  with  glass 
prisms ;  it  can  light  an  arc  of  225°,  leaving  the  ship  almost 
entirely  in  shade.  The  regulator,  on  the  Serrin  system,  is 
suspended  from  a  dial-plate.  A  small  seat  placed  in  the  top 
of  the  tower  makes  it  easy  for  the  watchman  to  regulate  the 
lamp  when  in  position.  The  beam  of  light  is  about  *80  metre 
across. 

"The  Gramme  machine  which  supplies  the  light  is  of  200 
carcels  power  ;  it  is  driven  directly  by  a  three-cylinder  Broth- 
erhood engine,  which  reduces  the  space  occupied  by  the  two 
machines  to  1'20  metre  in  length,  and  '65  and  '60  metre  in 
breadth  and  height  respectively.  These  two  machines  are 
placed  upon  a  false  flooring  in  the  engine-room,  about  40  metres 
from  the  lantern. 

"All  the  wires  pass  through  the  captain's  state-room,  who 
has  under  his  hands  switches  which  enable  him  to  cut  off  at 
will  the  light  from  the  lamp  in  the  tower,  or  from  a  second 
movable  lamp — of  which  we  shall  speak  further  on — and 
all  this  without  interrupting  the  running  of  the  Gramme 
machine. 

"The  novelty  in  the  arrangements  of  the  Amerique  con- 
sists in  the  automatic  intermittence  of  the  light  in  the  tower- 
lamp.  This  effect  is  obtained  by  a  very  simple  commutator, 
placed  on  the  extremity  of  the  arbor  of  the  Gramme  machine, 
and  which  sends  alternately  the  current  into  the  lamp  or  into 


402  APPLICATIONS   OF  THE  ELECTRIC  LIGHT. 

a  closed  metallic  coil  of  the  same  resistance  as  the  voltaic  arc, 
which  coil  is  heated  and  cooled  alternately.  This  arrange- 
ment has  been  adopted  to  leave  the  Gramme  machine,  which 
always  turns  850  times  a  minute,  in  the  same  conditions  in 
relation  to  the  exterior  circuit.  According  to  the  calculations 
of  M.  Pouzalz,  the  best  ratio  between  the  eclipses  and  flashes 
of  light  is  produced  by  a  light  of  20  seconds  duration  and  an 
eclipse  of  100  seconds. 

"The  light  is  ten  metres  above  the  sea-level,  and  the  possi- 
ble range  of  the  light,  with,  regard  to  the  depression  of  the  hori- 
zon, is  ten  geographical  miles  (18,520  metres)  for  an  observer 
whose  eye  is  six  metres  above  the  level  of  the  water. 

"For  the  purpose  of  lighting  the  topsails  and  top-gallant 
sails,  leaving  the  lower  sails  in  darkness,  M.  Pouzalz  con- 
structs a  galvanized  iron  cone,  and  places  it  over  a  movable 
lamp,  the  large  end  being  upward.  In  this  way  the  Amerique 
could  be  seen  a  long  distance  off  by  ships  and  telegraph  sta- 
tions, when  the  commander  chose  to  leave  the  light  in  action 
during  the  whole  night." 

This  last  described  light,  resembling  the  "plume"  light- 
houses, can  above  all  be  of  incontestable  service,  as  no  one 
can  find  any  fault  with  it.  As  much  could  not  be  said  for  the 
horizontal  projection,  which  was  assailed  with  criticisms  al- 
ready made  against  the  first  electric  lighting  of  1867  to  1870. 
This  enormous  light,  it  was  said,  would  be  confounded  with 
light-houses  by  other  ships,  and  would  be  liable  to  take  them 
from  their  course.  Again,  its  glare  caused  the  disappearance 
of  the  regulation  green  and  red  lights,  placed  on  right  and  left 
of  each  ship  to  indicate  its  course  in  the  darkness  to  other 
vessels,  and  new  chances  of  collision  would  result  therefrom. 
Finally,  it  was  said  that  the  electric  light  dazzled  the  ship's 
officers,  and  prevented  them  from  seeing  obstacles  ahead  as 
well  as  they  would  have  seen  them  without  it. 

To  these  objections  responses  were  not  wanting.  It  was 
easy  to  give  to  the  light  of  the  ships  an  altogether  different 
character  from  that  of  light-houses.  By  elevating  them  suf- 
ficiently above  the  deck,  the  starboard  and  port  lights  would 
not  be  interfered  with.  Finally,  after  having  tried  it,  the 
captain  of  the  ship,  M. .  Pouzalz,  formally  declared  in  his 
report  that  the  light  produced  by  short  flashes  had  never 
troubled  the  sight  of  any  officer  of  the  deck,  nor  of  the  watch- 
men on  the  bow,  and  that  the  glare  of  the  side-lights,  red 


THE  ELECTRIC   LIGHT  IN  WAR   AND   NAVIGATION.        403 

and  green,  was  not  diminished  by  the  use  of  the  forward 
light-house. 

Another  captain,  M.  de  Bacande,  was  no  less  satisfied  than 
M.  Pouzalz,  and  a  similar  electrical  plant  was  placed  upon 
another  transatlantic  ship.  In  spite  of  all  this,  routine  pre- 
vailed, and  these  two  plants  have  disappeared  after  some 
years'  service,  as  the  others  had  done,  under  the  indifference 
of  the  captains  who  were  obliged  to  keep  them  in  order. 

But  it  was  not  thus  in  other  countries,  where  a  certain 
number  of  steamships  possess  to-day  lighting  apparatus  sup- 
plied by  Gramme  machines ;  notably  the  packet-ships  of  the 
Austrian  Lloyds,  and  a  certain  number  of  English,  Danish, 
Russian,  and  other  vessels.  A  great  part  of  these  lighting- 
apparatus  are  French  in  origin,  and  came  from  the  factory  of 
MM.  Sautter  and  Lemonnier,  in  Paris.  The  Siemens  establish- 
ment, in  Berlin,  has  also  furnished  a  considerable  number. 

In  spite  of  the  opposition  encountered  by  electric  appa- 
ratus in  the  commercial  marine,  it  is  probable  that  they  will 
soon  come  into  use,  because  of  the  increasing  danger  of  col- 
lisions at  night,  so  dreadful  in  the  case  of  iron  ships,  that 
leave  no  floating  wreck  to  serve  as  a  life-preserver  for  the 
shipwrecked  people.  The  sea,  which  seems  so  vast,  is  much 
smaller  than  it  appears  so  far  as  navigation  is  concerned,  as 
the  whole  of  its  expanse  can  not  be  used.  It  is  furrowed  by 
actual  routes,  which  ships  from  various  motives  are  obliged  to 
follow  exactly,  and  which  become  at  last  as  crowded  as  a  rail- 
road when  commerce  is  very  active — for  example,  on  the  line 
between  Liverpool  and  New  York.  It  is  absolutely  necessary, 
in  this  case,  that  ships,  continually  increasing  in  speed,  shall 
see  each  other  from  a  distance  to  avoid  colliding.  It  will  soon 
be  conceded  that  the  electric  light  alone  can  give  this  result 
in  stormy  weather,  so  frequent  in  the  North  Atlantic. 

Although  more  distrustful,  and  slower  in  taking  up  the 
electric  light  than  the  merchant  marine,  the  French  navy  has 
been  more  faithful  to  it.  The  experiments  made  in  1877  on 
the  Suffren  and  Richelieu  quickly  brought  about  the  general 
introduction  of  projection-apparatus  as  a  means  at  once  of 
nautical  lighting  and  of  defense.  But  in  the  ensuing  year 
Colonel  Mangin's  projectors,  invented  for  army  use,  were  sub- 
stituted for  the  lenticular  projectors  hitherto  employed,  and 
the  navy  has  nearly  a  hundred  copies  of  this  particular  ap- 
paratus. 


404       •          APPLICATIONS   OF   THE   ELECTRIC   LIGHT. 

On  board  the  Suffren  and  Richelieu,  only  one  projector 
was  introduced,  placed  upon  the  captain's  bridge,  and  rolling 
from  port  to  starboard  upon  special  rails,  so  as  to  explore  at 
will  upon  either  side  of  the  vessel.  To-day  the  necessity  is 
recognized  of  lighting  when  desired  both  sides  of  the  vessel 
at  the  same  time. 

Large  armored  vessels  and  cruisers  now  require  two  pro- 
jectors for  each  one,  port  and  starboard,  at  the  ends  of  the 
captain's  bridge  or  a  little  below  it.  But  there  is  only  one 
electric  generator,  a  Gramme  machine,  whose  current  can  sup- 
ply one  or  the  other  of  the  projectors  by  the  movement  of  a 
switch  placed  under  the  hand  of  the  captain  or  officer  of  the 
deck.  Rapid  as  this  movement  may  be,  it  is  preferable  to 
have  two  machines,  so  that  the  lighting  of  both  sides  of  the  ship 
shall  be  really  simultaneous.  This  arrangement  is  adopted 
in  the  navy  of  other  countries,  especially  of  England,  Austria, 
Denmark,  and  Italy  ;  the  two  Gramme  machines  used  are  then 
connected  so  that  both  projectors  can  be  lighted  at  once,  or 
their  whole  power  be  concentrated  upon  a  single  apparatus. 

When  the  ship  has  only  a  single  projector,  its  proper  place 
is  well  forward,  as  in  the  Russian  ship,  the  Livadia.  It  would 
be  still  better  to  carry  it  upon  a  special  platform  running  out 
over  the  bow,  as  M.  Dalman  arranged  it  upon  the  Spanish 
armored  ships,  Numancia  and  Vitoria. 

Apparatus  similar  to  those  of  the  large  ships  have  been 
established  in  the  principal  ports  of  France  to  light  the  courses 
on  which  an  enemy's  fleet  would  approach.  When  the  chan- 
nel is  two  kilometres  wide,  two  projectors  at  once  are  used  to 
light  the  whole  of  it.  Most  of  the  European  nations  have 
adopted  similar  arrangements,  and  exhaustive  experiments 
were  made  in  several  countries  between  1878  and  1881  to  ascer- 
tain the  range  and  efficacy  of  these  new  means  of  defense. 
We  shall  especially  cite  the  experiments  in  the  Gulf  of  Jouan, 
at  Toulon,  and  Cherbourg  in  France,  those  at  Chatham  in 
England,  Pola  in  Austria,  and  Cronstadt  and  the  camp  of 
Valkof  in  Russia,  etc. 

These  experiments  have  shown  that  with  a  powerful  and 
concentrated  beam  of  light  (4,000  carcels)  persons  placed  near 
the  projectors  could  distinguish,  with  opera-glasses,  white 
houses  seven  kilometres  distant.  Under  similar  conditions,  a 
fort  or  war-ship  three  kilometres  distant  could  be  lighted, 
by  throwing  upon  it  a  beam  of  light  three  hundred  metres 


THE  ELECTRIC   LIGHT  IN   WAR  AND   NAVIGATION.        405 

wide,  when  the  embrasures  could  be  easily  discerned.  Finally, 
at  this  same  distance  of  three  kilometres,  the  red  buoys  which 
indicate  a  channel,  or  similar  objects,  could  be  made  visible. 

The  new  apparatus  were  also  well  tried  in  the  North  Sea 
during  the  Turco- Russian  war.  The  ports  of  Odessa,  Sebas- 
topol,  and  Orchakow  were  thus  secured  against  surprise  by 
the  enemy.  The  port  of  Odessa  especially,  supplied  with  a 
Mangin  projector,  operated  by  a  Gramme  machine,  could  with 
certainty  show  at  night,  four  or  five  kilometres  distant,  large 
ships  coming  to  attack  it.  Low-built  vessels,  painted  in  dark 
colors,  escaped  the  sight  for  longer  periods,  but  they  even 
were  seen  two  kilometres  off.  The  German  apparatus,  placed 
in  the  other  ports,  had  one  third  less  range. 

Great  as  their  power  may  be,  electric  projectors  would  not 
suffice  to  protect  armored  ships  against  the  attack  of  torpedo- 
boats.  These  are,  in  fact,  very  well  concealed  under  a  general 
black  color,  which  covers  even  the  figures  of  the  sailors,  as 
they  are  dressed  in  the  universal  black.  In  these  conditions, 
the  most  that  can  be  hoped  for  is  to  see  the  torpedo-boat  five 
hundred  metres  away,  and  then  it  is  too  late  to  elude  it.  The 
best  means  of  avoiding  the  danger  is  to  protect  the  ships  at 
a  distance  by  steam  launches,  which  patrol  on  all  sides  like 
the  pickets  of  a  camp. 

But  to  keep  up  this  surveillance  on  all  sides,  the  launches 
need  also  electric  projectors,  and  they  can  only  carry  small 
ones.  For  them  very  small  ones  (thirty  centimetres  in  diam- 
eter) have  been  designed,  which  weigh  only  one  hundred  and 
sixty  kilogrammes  with  their  accessories.  The  Gramme  ma- 
chine which  supplies  them  can  be  driven,  on  an  emergency, 
by  four  men,  without  any  steam  motor ;  but  it  must  be  un- 
derstood that  they  are  also  provided  with  a  Brotherhood 
engine. 

In  spite  of  their  reduced  dimensions,  these  apparatus  have 
still  great  power,  for  their  range  extends  to  4wo  kilometres 
when  the  night  is  clear.  It  will  be  understood  that  we  speak 
of  the  range  for  ordinary  objects,  of  light  colors  and  pretty 
large  size.  The  torpedo-boats,  painted  black,  would  only  be 
seen  some  hundreds  of  metres  distant.  Furthermore,  the 
torpedo-boats  themselves  have  a  similar  plant,  which  costs 
about  six  thousand  francs. 

The  picket-boats  and  gunboats  have  a  more  powerful  ap- 
paratus that  costs  nearly  ten  thousand  francs,  and  sometimes 


406  APPLICATIONS   OF   THE  ELECTRIC   LIGHT. 

they  have  two  projectors,  like  the  large  armored  ships,  which 
brings  up  the  expense  to  more  than  sixteen  thousand  francs. 

The  use  of  powerful  electric  lights  in  naval  tactics  is  far 
too  recent  for  it  to  be  known,  as  yet,  all  the  use  that  can  be 
made  of  them,  or  all  the  manoeuvres  in  which  they  can  be 
employed.  A  number  of  very  interesting  features  in  their 
operations  have,  however,  been  observed.  We  give  some  ex- 
amples : 

When  not  too  far  off,  the  best  method  of  discerning  an 
object — a  suspected  embarkation,  for  instance — is  not  to  light 
it  directly.  The  light  should  rather  be  projected  above  it. 
The  particles  of  water  and  of  solid  matter  always  present  in 
the  air  reflect  the  luminous  rays  upon  the  suspected  party, 
and  make  it  very  visible.  If,  on  the  other  hand,  the  beam  of 
light  falls  upon  the  sea  in  front  of  the  object  sought  for,  it 
will  completely  disappear  from  view.  This  is  because  the 
rays  of  light  are  reflected  from  the  surface  of  the  water,  and 
form,  as  they  rise  again,  a  sort  of  luminous  veil  that  conceals 
the  object  sought  for.  This  is  due  to  a  general  law.  The 
eye  can  not  penetrate  a  beam  of  intense  light.  In  this  may 
be  found  a  means  of  hiding  certain  manoeuvres  from  the 
enemy  behind  a  curtain  of  light,  just  as  the  movements  of 
troops  are  now  hidden  behind  a  curtain  of  cavalry. 

The  luminous  ray  can  constitute  for  the  enemy  a  very 
great  embarrassment,  and  can  even  paralyze  his  movements. 
It  has  been  remarked,  in  fact,  that  a  party  of  men  surprised 
suddenly  by  the  projection  upon  them  of  the  luminous  beam, 
become  incapable  of  manoeuvring  for  some  time  at  least. 
This  is  because  men  who  have  been  some  time  in  darkness  are 
blinded  by  a  sudden  light. 

The  role  of  the  electric  light  in  optical  telegraphy,  on  land 
or  on  sea,  must  now  be  spoken  of.  In  this  it  plays  no  part 
except  a  source  of  intense  light,  and  the  mechanism  used  in 
optical  telegraphy  has  no  direct  relation  with  the  electric 
light.  In  principle,  too,  this  mechanism  is  very  simple.  It 
is  known  to  our  readers  that  in  ordinary  telegraphy  the  Morse 
alphabet  expresses  all  the  letters  of  the  alphabet  by  dots  and 
dashes  variously  combined.  The  same  signals  are  employed 
in  optical  telegraphy ;  but,  instead  of  tracing  them  upon 
paper,  they  are  written  in  the  air  with  flashes  of  light ;  the 
dots  are  instantaneous  flashes,  the  lines  are  flashes  of  light 
having  a  certain  duration.  Here  it  will  be  seen  is  a  mechan- 


THE  ELECTRIC  LIGHT  IN  THE   THEATRE.  407 

ism  analogous  to  that  producing  the  signals  of  light-houses. 
It  works  very  well  with  petroleum  lamps.  But,  when  the 
source  of  light  is  more  intense,  the  range  naturally  increases 
in  proportion,  which  is  of  importance,  especially  in  bad 
weather.  It  is  in  this  regard  that  the  electric  light  is  particu- 
larly available  in  this  application.  As  there  is  in  these  cases 
generally  no  need  of  a  large  quantity  of  light,  in  the  army  a 
very  light  Gramme  machine,  driven  by  four  men  who  turn  a 
crank  like  that  of  a  rotary  pump,  is  considered  ample. 

Thanks  to  the  labors  of  Colonel  Laussedat,  to-day  director 
of  the  Conservatoire  des  Arts  et  Metiers,  in  Paris — labors  pur- 
sued subsequently  by  Colonel  Mangin — optical  telegraphy 
works  very  well  at  the  present  day  in  France.  By  means  of 
it,  it  may  be  specially  noted  here,  during  the  campaigns  of 
Southern  Oran  and  Tunis,  the  news  of  the  entry  of  military 
forces  into  the  heart  of  the  Sahara  was  transmitted  to  Paris 
in  a  few  hours,  several  hundred  kilometres  intervening  be- 
tween the  nearest  telegraph  station  and  the  scene  of  opera- 
tions. Using  this  system,  a  besieged  place,  such  as  Paris  in 
1870,  could  often  communicate  over  the  heads  of  the  assail- 
ants, without  fearing  any  revelation  of  the  dispatches  to  the 
enemy.  In  such  a  country  as  the  Algerian  Sahara,  its  impor- 
tance is  still  greater,  because  it  is  enough,  if  a  certain  number 
of  distant  fortified  places  are  occupied,  to  be  almost  instantly 
informed  of  what  is  passing  at  the  extreme  limit  of  our  lines, 
without  attempting  the  almost  impossible  task  of  guarding  a 
telegraphic  wire  in  the  desert. 


CHAPTER  III. 

THE  ELECTRIC  LIGHT  IN  THE  THEATRE. 

ALTHOUGH  the  electric  light  was  first  used  industrially — 
to  any  extent,  at  least — in  light-houses,  it  is  in  another  field, 
in  the  theater,  that  it  made  its  debut  into  practical  life,  it  may 
even  be  said  into  industrial  life,  as  it  does  not  work  there  for 
nothing.  It  appears  to  have  been  in  a  fairy  piece,  entitled 
"The  Sick  Potatoes,"  that  it  made  its  first  appearance  before 
the  French  public ;  but  we  are  ignorant  of  the  role  it  there 
played. 


408 


APPLICATIONS  OF  THE  ELECTKIC  LIGHT. 


A  little  later,  in  1846,  it  was  applied  with  great  splendor 
in  the  famous  opera,  "The  Prophet,"  where  it  had  to  repre- 
sent the  rising  sun.  The  effect  of  the  rising  sun  was  obtained 
by  the  use  of  a  parabolic  mirror  (Fig.  238),  which  brought  all 
the  rays  into  parallelism,  and  projected  a  cylindrical  beam  of 
light  upon  a  silken  screen,  where  it  produced  perfectly  the 

image  of  a  disk.  The 
apparatus  was  made  to 
rise  back  of  curtains 
so  arranged  as  to  hide 
its  mechanism  from  the 
audience,  and  thus  pro- 
duced the  complete  il- 
lusion of  the  sunrise. 

M.  J.  Duboscq,  the 
co-laborer  of  Foucault, 
was  the  first  who  super- 
intended the  introduc- 
tion of  the  electric  light 
upon  the  stage  of  the 
Grand  Opera  of  Paris. 
In  1855  he  was  finally 
put  in  permanent  charge 
of  a  service,  which  is 

Fw.  238.-Apparatus  used  in  "The  Prophet,"  to        Stl11    1Q     ^1S    Car6>     and> 

represent  the  sun.  five  years  later,  on  the 

occasion  of  the  repro- 
duction of  the  opera  of  "Moses,"  he  produced  for  the  first 
time  a  real  rainbow. 

It  is  known  how  important  a  part  the  rainbow  plays  in 
this  opera,  at  the  moment  when  the  waves  of  the  Red  Sea  are 
closing  in  behind  the  Hebrews  to  engulf  the  pursuing  army  of 
Pharaoh.  Previous  to  this  the  rainbow  had  been  represented 
by  colored  bands  of  paper  stretched  upon  a  large  blue  cloth, 
which  represents  in  the  background  the  sky  of  Egypt.  To 
make  it  appear  at  the  proper  moment,  large  lamps  are  lighted 
behind  it,  which  can  hardly  be  made  to  supply  a  light  sensi- 
bly greater  than  that  of  the  scene.  To  make  this  rainbow 
come  out,  the  general  light  has  to  be  reduced,  as  if  night 
was  coming  upon  the  scene.  The  miracle  thus  becomes  a 
little  too  great,  even  for  the  remote  epoch  where  it  is  placed, 
because  the  rainbow  appears  in  full  night  before  spectators 


THE   ELECTRIC   LIGHT   IN   THE   THEATRE. 


409 


well  informed  of  the  fact  that  it  is  due  to  decomposition  of 
the  rays  of  the  sun. 

The  electric  light  furnished  M.  J.  Duboscq  the  means  of 
producing  a  rainbow  bright  enough  to  be  seen  with  the  scene 
fully  lighted,  and  which  is,  moreover,  a  true  rainbow,  obtained 
by  the  identical  processes  of  real  nature.  We  give  the  de- 
scription of  the  apparatus  according  to  M.  Saint-Edme  : 

The  electrical  apparatus,  whose  arc  is  supplied  by  one 
hundred  Bunsen  cups,  is  placed  upon  a  scaffold  of  suitable 
height,  five  metres  from  the  curtain,  and  perpendicular  to  the 
cloth  which  represents  the  sky  upon  which  the  rainbow  is  to 
appear.  The  whole  optical  apparatus  is  fitted  for  and  kept  in 
a  blackened  box,  which  permits  no  light  to  escape  into  the 
air  (Fig.  239).  The  first  lenses  give  a  parallel  system  of  rays, 

which  passes  next  through 
a  screen  with  an  opening 
in  the  shape  of  an  arc. 
This  beam  is  received  by  a 
double-convex  lens  of  very 
short  focus,  which  plays 
the  double  rdle  of  increas- 
ing the  curvature  of  the 
image  and  of  giving  it  a 
greater  extension.  As  they 
leave  this  last  lens,  the 
rays  of  light  pass  through 
the  prism  arranged  to  de- 
compose them,  and  conse- 
quently produce  the  rain- 
bow. The  position  of  the 
prism  is  not  a  matter  of 
indifference ;  its  summit 
must  be  upward,  referred 
to  the  incident  beam,  with- 
out which  the  colors  of  the 
arc  would  not  be  displayed 
upon  the  receiving  screen 

in  the  same  order  which  follow  in  the  rainbow.  By  the  use 
of  this  system  the  rainbow  appears  luminous  even  when  the 
stage  is  brightly  lighted.  We  have  endeavored  to  reproduce 
its  effect  in  Fig.  240. 

The  rainbow  is  not  the  only  meteorological  phenomena 


Fia.  239.— Apparatus  for  the  production  of  the 
rainbow  on  the  stage. 


410 


APPLICATIONS   OF  THE  ELECTRIC   LIGHT. 


which  it  is  desirable  to  reproduce  upon  the  stage.  The  storm, 
especially,  appears  so  often  in  pieces  of  all  classes  that  it  is 
important  to  know  how  to  accurately  reproduce  it. 

The  noise  of  thunder  can  easily  be  imitated  in  the  theater ; 
the  " properties"  comprise  always  a  tom-tom  and  a  sheet  of 
elastic  metal  designed  for  this  use.  ;  but  what  is  not  so  easy  is 
to  produce  upon  the  stage  flashes  of  lightning  having  more 
resemblance  to  the  real. 

In  early  days,  to  imitate  the  phenomenon,  the  cloth  of  the 
back  scene  was  lighted  up  from  behind  by  a  flame  colored 


FIG.  240.— The  rainbow  in  the  opera  of  u  Moses." 

red,  a  narrow,  sinuous  opening  being  made  in  the  canvas. 
The  art  of  scenery  advancing  with  the  progress  of  science,  it 
became  necessary  to  do  better,  and  the  choice  of  a  source  of 
light  naturally  fell  upon  the  voltaic  arc,  whose  origin  is  iden- 
tical with  that  of  lightning.  But  more  was  necessary  ;  an 
optical  arrangement  was  required  which  would  give  the  power 
of  emitting  and  extinguishing  the  luminous  ray  at  short  in- 
tervals, and  at  the  same  time  of  giving  it  the  characteristic 
zig-zag  movement  of  lightning.  For  this  end  M.  J.  Duboscq 


THE   ELECTRIC   LIGHT   IN  THE   THEATRE. 


411 


had  recourse  to  a  species  of  magic  mirror  (Fig.  241),  in  front 
of  which  was  placed  the  electric  light. 

The  mirror  is  concave,  and  the  luminous  point  corresponds 
with  its  focus.  The  upper  carbon  electrode  is  stationary,  but 
the  lower  carbon  can  receive  at  any  given  moment  a  move- 
ment of  separation  which  lights  the  apparatus.  This  same 
effect  can  be  produced  by  electro-magnetic  attraction.  As 
the  mirror  is  held  in  the  hand,  it  is  easy,  by  shaking  it,  and 
using  a  switch,  to  imitate  quite 
well  the  zig-zags  of  lightning 
and  their  sudden  apparition. 

The  name  of  magic  mirror 
has  been  given  to  this  appa- 
ratus, because  its  small  dimen- 
sions enable  it  to  be  held  by 
one  of  the  actors,  who  can  pro- 
duce many  useful  effects  with 
it,  especially  in  fairy  scenes. 
It  was  for  this  particular  end 
that  it  was  invented,  and  it  was 
shown  for  the  first  time  in  the 
theater  of  the  Varietes,  in  Paris, 
in  a  play  called  "The  Travels 
of  Truth."  Wires  hidden  in 
the  sleeves  of  the  actor  con- 
ducted the  electric  current,  and 
a  small  key  placed  under  the 
actor's  finger  lighted  the  apparatus.  It  is  easy  to  imagine 
the  varied  scenic  effects  that  could  be  thus  produced. 

The  incidents  of  the  action,  especially  in  operas  and  fairy 
pieces,  require  sometimes  a  strong  ray  of  light  to  follow  a 
personage  through  all  his  movements.  The  ordinary  appa- 
ratus are  too  bulky  and  hard  to  move  for  this  purpose.  M.  J. 
Duboscq  has  invented  lighter  ones,  provided  with  the  neces- 
sary joints  to  direct  the  luminous  rays  in  all  directions,  and 
which,  moreover,  can  be  hung  upon  the  wall. 

This  apparatus  (Fig.  242)  is  composed  of  a  wooden  or 
sheet-iron  lantern  containing  the  electric  lamp,  whose  light 
emerges  through  lenses  which  make  it  possible  to  concentrate 
all  the  rays  upon  a  single  point.  This  point  can  be  enlarged 
or  contracted  at  pleasure  by  the  movements  of  a  special  dia- 
phragm which  limits  the  field  of  lighting. 


FIG.  241. — Magic  mirror  for  the  produc- 
tion of  lightning  in  the  theatre. 


412 


APPLICATIONS   OF  THE   ELECTPJC   LIGHT. 


FIG.  242.— Electric  lamp  for  illuminating 
an  actor  in  the  play. 


When  larger  surfaces  have  to 
be  lighted,  as  a  panel  of  a  wall 
or  the  corner  of  a  garden,  an- 
other apparatus  (Fig.  243)  is 
used,  also'  articulated  in  all  di- 
rections, but  whose  light  is  con- 
centrated by  a  large  enough  mir- 
ror of  silvered  glass  instead  of 
a  lens. 

We  could  cite  numerous  in- 
stances of  such  applications  in 
well-known  operas.  It  will  be 
enough  to  reproduce  one  of  the 
scenes  in  the  opera  of  "Moses," 
where  the  principal  personage 
is  thus  lighted  by  the  luminous 
rays  (Fig.  244). 

Among  the  other  applica- 
tions of  the  electric  light  in  the 

theater,  one  of  the  most  used  and  most  applauded  is  the 

luminous  fountain. 

When  a    liquid    escapes 

from  a  vessel  by  a  circular 

orifice,  the  jet  takes  the  form 

of  a  parabola  ;  moreover,  the 

liquid  vein  is  not  absolutely 

cylindrical;  it  is  contracted 

at  a   point  whose    distance 

from   the   orifice    is   mathe- 
matically determinable.     In 

consequence  of  this,  if  a  ray 

of  light  is  directed  upon  the 

orifice    of    escape,   it   seems 

drawn  along  by  the  liquid, 

and  follows  it  in  all  parts  of 

its  course. 

The  phenomenon  is  desig- 
nated in  optics  by  the  name 

of  total  reflection ;  on  account 

of  the  curvature  of  the  liquid 

vein,  the  beam  is  reflected  at     Fio  243<_EIectric  lamp?  with  rairror,  for 

eacn  point    OI   its    COUrse    by  lighting  a  particular  point  of  the  scene. 


THE  ELECTRIC  LIGHT   IN   THE   THEATRE. 


413 


the  molecules  which  it  meets,  and,  instead  of  escaping  from  it 
into  space,  it  is  reflected  onward  by  the  molecules  in  the  direc- 
tion of  the  jet,  which  takes  the  appearance  of  a  jet  of  fire. 
If  the  liquid  curve  be  broken,  the  phenomenon  of  reflection 
ceases,  and  flashes  of  light  play  around  the  point  of  inter- 
ruption. 

The  water  is  placed  in  a  cylindrical  prismatic  vase  of  con- 
siderable height.  The  electric  lamp,  supplied  for  this  pur- 
pose with  a  system  of  lighting  lenses,  is  placed  in  front  of  an 


FIG.  244.— Scene  in  the  opera  of  "  Moses." 


orifice  closed  by  a  pane  of  transparent  glass,  so  directed  that 
the  luminous  ray  shall  enter  the  arc  of  curvature  formed  by 
the  water  as  it  escapes.  By  placing  colored  glasses  in  front  of 
the  electrical  apparatus,  the  color  of  the  jet  is  changed  at  will. 
In  1853  the  first  luminous  fountain  was  shown  in  the  opera 
at  Paris,  in  the  ballet  of  "Elia  and  My  sis."  Every  one  has 
seen,  in  the  second  act  of  "Faust,"  the  fountain  which  Me- 
phistopheles  causes  to  play,  and  whose  nature  he  subse- 
quently changes.  It  works  upon  this  principle.  It  is  one  of 
the  first  ever  used,  and  it  has  been  followed  by  many  others, 


APPLICATIONS   OF  THE  ELECTRIC   LIGHT. 

in  all  kinds  of  theaters.  They  now  make  them  much  stronger 
and  more  beautiful.  In  grand  spectacular  pieces  immense 
cascades  are  often  illuminated  which  sometimes  fall  almost  in 


FIG.  245. — Luminous  fountain. 

a  semicircle.  When  fountains  are  alone  to  be  used,  fountains 
playing  in  the  air  and  falling  back  like  those  in  our  public 
parks  (Fig.  245)  are  generally  used. 

We  could  cite  many  other  applications  of  the  electric  light 
to  theatrical  machinery.  Whenever  an  extremely  intense 
light  is  required  to  obtain  a  certain  effect,  the  electric  light  is 
called  upon. 

This  happens  especially  in  the  case  of  apparitions  of  spec- 
ters in  the  midst  of  the  characters  upon  the  stage — appari- 
tions that  always  produce  a  good  effect  when  they  are  well 
managed.  These  spectres  are  living  people,  placed  below  the 
level  of  the  stage,  generally  near  the  prompter's  box.  Their 
image  is  reflected  on  a  piece  of  plate-glass,  placed  on  the 
stage  and  inclined  at  an  angle  of  45°.  The  clear  glass  can 
not  produce  images  except  by  receiving  upon  one  of  its  faces 
a  much  more  powerful  light  than  on  the  other.  This  is 


THE  ELECTRIC  LIGHT  IN  THE  THEATRE.  415 

effected  by  lighting  with  a  strong  electric  light  the  characters 
who  are  to  become  spectres  in  the  glass. 

Besides  the  uses  of  the  electric  light  which  we  have 
pointed  out  as  accessory  in  theatrical  representations,  there  is 
another  much  more  important,  and  to  which  the  terrible  acci- 
dents which  have  recently  occurred  in  Nice  and  Vienna  give 
the  greatest  importance  ;  we  speak  of  the  substitution  of 
electric  lighting  for  gas-lighting.  The  chances  of  fires,  the 
insupportable  production  of  heat  and  foul  air,  finally,  the 
rapid  deterioration  of  all  the  decorations,  are  serious  faults 
of  the  latter,  from  which  its  rival  is  exempt. 

Its  advantages  are  so  great,  that  it  would  doubtless  have 
been  everywhere  adopted  already,  if  this  were  as  easy  as 
supposed.  This  we  must  briefly  examine,  if  only  to  indi- 
cate the  way  to  follow  in  pursuing  experiments  upon  this 
subject. 

The  principal  parts  of  a  theatre  to  be  lighted  are  the  vesti- 
bule and  main  stairway,  the  auditorium,  the  stage,  and^he 
lobby.  From  the  point  of  view  of  lighting,  these  places  are 
not  as  independent  as  might  be  supposed ;  a  fixed  relation 
between  them  must  be  maintained,  a  skillful  graduation,  and 
for  this  end  a  single  system,  too  feeble  for  the  one  and  too 
strong  for  the  other,  would  not  answer.  The  lighting  of  the 
lobby  seems  easy,  and  yet  we  have  seen  that  at  the  Opera  two 
different  systems  are  needed  for  the  lobby :  a  moderate  light 
for  the  people  promenading  there ;  powerful  lights  of  warm 
colors  to  reach  the  ceiling  and  bring  out  the  paintings,  which 
are  its  principal  ornament. 

The  vestibule  and  stairs  are  easily  lighted,  and  if  advan- 
tage be  taken  of  this  to  waste  the  light,  the  other  places  near 
it  will  seem  obscure.  If  the  auditorium  be  lighted  as  brill- 
iantly as  this  place,  what  will  become  of  the  stage  ?  In  the 
auditorium,  the  chandelier  can  not  well  be  dispensed  with, 
not  only  as  a  matter  of  decoration,  but  also  because  it  is  really 
the  necessary  and  natural  radiating  point  of  the  luminous 
rays,  which  have  to  diffuse  the  necessary  light  under  all  the 
ceilings  of  the  different  galleries.  The  bad  effect  of  luminous 
ceilings  on  which  many  hopes  were  founded  has  not  been  for- 
gotten ;  at  the  Opera,  the  luminous  circle  formed  by  cut-glass 
globes,  placed  in  the  cornices  and  lighted  with  electric  candles, 
has  shown  that  the  chandelier  could  be  assisted  by  the  for- 
mation, at  this  height,  of  a  network  of  powerful  light  which 

28 


416  APPLICATIONS   OF  THE  ELECTRIC  LIGHT. 

is  effectively  reflected  by  the  ceiling.  It  is  at  the  same  time 
very  decorative. 

But,  assuming  all  this  to  be  settled,  the  stage  remains  to 
be  provided  for,  and  it  is  enough  to  have  examined  it  near 
at  hand  to  understand  the  difficulty.  Here  the  electric  light 
must  be  more  pliant  and  obedient  than  elsewhere.  The  act- 
ual gas  apparatus  are  the  fruit  of  long  study,  and  electricity 
can  only  replace  it  light  by  light,  on  the  condition  that  it  can 
accommodate  itself  to  the  graduations  on  which  all  possible 
effects  depend. 

To  all  this  must  be  added  the  necessity  of  generating  the 
electricity,  by  the  aid  of  machines,  at  a  distance  from  the 
theatre,  which  has  already  without  this  enough  other  causes 
of  fire  and  accidents ;  the  absolute  necessity  of  organizing 
the  service  so  as  to  avoid  all  possible  chance  of  extinctions, 
accidental  or  premeditated,  or  at  the  least  to  make  them  of 
little  account  by  confining  them  to  a  restricted  range ;  and  all 
this  without  speaking  of  the  expense,  which  can  be  supported 
by  national,  subsidized  theatres,  but  which  would  be  beyond 
the  resources  of  others. 

The  conclusion  must  be  that  the  electric  light  and  gas-light 
have  to  be  introduced  under  the  same  conditions.  When 
works  of  large  capacity  distribute  electricity,  and  when  the 
consumer  can  have  a  constant  and  regular  supply  and  lights 
of  all  degrees  of  intensity  without  extinctions  or  inconveni- 
ences, it  can,  in  the  natural  course  of  things,  be  introduced 
into  our  theatres,  which  can  not  be  expected  to  generate  their 
lighting  current  any  more  than  it  would  be  supposed  practic- 
able to  annex  a  special  gasworks  to  them. 

To  realize  this  improvement,  whose  urgency  admits  of  no 
debate,  a  vast  amount  of  study  and  experimentation  has  to 
be  gone  through  with.  As  for  employing  the  electric  light 
as  an  auxiliary  of  gas,  this  is  a  half  solution,  which  adds  the 
difficulties  of  the  one  to  the  inconveniences  of  the  other.  It 
can  only  be  tolerated  as  a  means  of  arriving  gradually  at  the 
complete  solution  of  the  varied  conditions  of  this  difficult 
programme,  which  must  be  solved  and  applied  by  the  man- 
agement itself. 

Outside  of  regular  theatres  properly  so  called,  on  whose 
account  experiments  are  still  being  prosecuted,  there  are  some 
of  a  much  simpler  kind,  and  for  which  the  electric  light  can 
furnish  at  the  present  time  a  light  superior  to  and  much 


INDUSTRIAL  APPLICATIONS.  417 

cheaper  than  that  of  gas.  We  shall  cite,  as  example,  the 
plant  which  has  worked  for  two  years  at  the  Hippodrome  of 
Paris  (Fig.  57).  This  immense  hall,  whose  area  is  6,300 
square  metres,  and  which  holds  8,000  spectators,  is  lighted 
by  the  aid  of  two  systems,  twenty  voltaic  arc-lamps,  and  one 
hundred  and  twenty  Jablochkoff  candles.  The  first  light  the 
ring ;  the  others  are  arranged  in  two  lines  on  the  circumfer- 
ence of  the  hall,  and  in  four  groups  around  the  columns 
that  sustain  the  edifice.  Two  steam-engines  of  one  hundred 
horse-power  drive  four  gramme  machines  of  twenty  Jabloch- 
koff candles,  twenty  gramme  machines  of  the  factory  type, 
and  one  sixty-candle  machine,  the  most  powerful  of  this  kind 
that  has  ever  been  built.  The  cost  of  the  plant  has  been  put 
at  200,000  francs  in  round  figures,  and  the  expense  per  night 
at  320  francs  for  a  light  equivalent  to  12,000  carcels.  Gas 
would  cost  for  the  same  light  1,200  to  1,500  francs. 


CHAPTER  IY. 

INDUSTRIAL  APPLICATIONS. 
I. 

WE  have  now  reached  the  most  important  question — as 
much  from  our  point  of  view  as  consumers  as  from  that  of 
the  development  of  this  new  application  of  science,  to  which 
so  much  energy  and  money  have  been  devoted— its  use  in  gen- 
eral lighting,  concurrently  with  the  other  methods  of  light- 
ing of  which  we  have  already  spoken,  and  which,  we  must  not 
cease  asserting,  have  much  more  to  gain  than  to  lose  by  its 
general  introduction. 

We  are,  fortunately,  not  obliged  to  speak  of  its  good  quali- 
ties. The  Electrical  Exhibition  at  Paris  has  succeeded  be- 
yond doubt  in  proving  to  the  most  incredulous  what  marvel- 
ous resources  it  places  in  our  hands,  and  what  a  varying 
amount  of  candle-power  we  can  obtain  from  it,  ranging  from 
two  or  three  candles  to  several  thousands  of  carcels  if  neces- 
sary. Steadiness,  coloration,  division  of  the  lights,  all  has 
been  realized  ;  it  is  easy  to  select  lights  the  most  appropriate 
for  the  conditions  to  be  filled,  and  only  the  question  of  ex- 


418  APPLICATIONS  OF  THE  ELECTRIC  LIGHT. 

pense  lias  to  be  thought  of.  It  is  true  that  this  last  consid- 
eration is  a  most  important  one,  and,  without  regard  to  the 
special  qualities  of  the  electric  light,  we  might  say  of  its  su- 
periority over  other  systems,  it  is  desirable  that  economy 
should  be  added  thereto — it  is  necessary,  in  a  word,  that  it 
should  be  both  better  and  cheaper. 

Unfortunately,  the  electric  light  does  not  come  within  ordi- 
nary conditions ;  we  have  not  got  electricity  at  our  disposal 
like  gas,  which  presents  itself  at  our  hand  without  our  need- 
ing to  give  a  thought  to  its  production.  This  may  be  in  the 
near  future — it  will  come  eventually  ;  on  that  day  electricity 
will  have  to  be  used  ;  all  discussion  will  cease.  Meanwhile, 
to  have  the  light,  the  electricity  must  be  generated  by  the 
consumer  ;  the  expense  of  establishment,  of  maintenance,  and 
the  sinking  fund,  must  be  advanced.  All  this  becomes  an 
element  of  much  importance  in  computing  the  cost  of  supply 
— an  element  which,  in  the  case  of  gas,  is  comprised  in  the 
selling  price,  and  which  does  not  weigh  heavily  on  the  con- 
sumer, as  it  is  spread  over  an  enormous  total  of  sales.  The 
importance  of  this  element  is  naturally  proportional  to  the 
number  of  hours  of  lighting.  This  is  not  much  for  cases 
where  it  is  needed  by  day  and  by  night,  as  in  certain  facto- 
ries and  some  departments  of  railroad  work ;  it  is  a  burden 
upon  a  business  that  only  needs  artificial  light  during  the 
evenings.  In  spite  of  this,  the  electric  light,  judiciously  used, 
is  even  now,  in  many  circumstances,  more  economical  than 
gas,  not  only  at  the  high  price  paid  for  it  in  Paris,  but  even 
at  the  reduced  price  given  to  the  municipalities  and  railroad 
companies,  and  even  at  the  still  lower  price  that  gas  is  sold 
at  in  coal-producing  regions. 

Since  the  year  1856,  when  experiments  with  the  electric 
light  were  first  begun — on  the  one  hand,  with  the  old  batter- 
ies, and  on  the  other  hand  with  the  Alliance  machine,  then 
making  its  debut— the  price  of  this  light  has  continually  di- 
minished. 

In  the  experiments  made  in  Lyons,  in  1857,  by  MM. 
Lacassagne  and  Thiers,  a  light  of  about  fifty  carcels,  pro- 
duced by  sixty  Bunsen  cups,  cost,  according  to  M.  Becquerel, 
three  francs  fifty-five  centimes  per  hour  ;  this  is  about  what  it 
would  cost  to-day  with  this  mode  of  production.  According 
to  experiments  made  in  the  Conservatoire  des  Arts  et  Metiers 
with  the  Alliance  machine,  in  1856,  M.  Leroux  found  as  the 


INDUSTRIAL  APPLICATIONS.  419 

cost  of  100  carcels  light,  the  figure  four  francs  thirty  centimes ; 
this  cost  refers  to  a  lighting  of  500  hours  per  annum,  and  we 
can  see  now  the  influence  of  the  number  of  hours  in  the 
figures  found  by  M.  Eeynaud  for  a  machine  of  the  same  sys- 
tem used  in  light-houses.  The  cost  of  maintaining  a  light  of 
230  carcels  is  reduced  to  one  franc  ten  centimes  per  hour. 

With  the  Gramme  machine  the  price  falls  still  lower.  A 
light  of  150  carcels,  used  for  a  lighting  of  500  hours  per  an- 
num, does  not  cost  more,  according  to  figures  obtained  by  M. 
Fontaine  from  its  first  applications  to  use,  than  one  franc 
ninety-two  centimes.  In  the  factory  of  M.  Manchon,  this  cost 
descends  to  one  franc  twenty-three  centimes,  and,  according 
to  M.  Picou,  in  another  plant  to  ninety-two  centimes. 

The  division  of  the  light  was  not  yet  perfected,  and  a 
special  machine  was  needed  for  each  light ;  nevertheless,  re- 
markable results  were  obtained  by  a  plant  set  up  in  1876  by 
the  Northern  Railroad  Company  for  lighting  its  freight  depot, 
and  the  principal  figures  of  which  have  been  published  by 
M.  Sartiaux. 

A  room  seventy  metres  square  and  eight  metres  high,  a 
shed  seventy  by  fifteen  metres,  of  the  same  height,  and  a 
court  twenty  metres  square,  separating  the  room  from  the 
shed,  had  to  be  lighted.  A  complete  small  plant  was  erected, 
including  the  house  and  motor,  with  counter-shafting,  six 
Gramme  machines,  five  working  and  one  in  reserve.  The  cost 
of  establishment  was  as  follows : 

Shed  area,  forty  square  metres  (430  square  feet).  2,200  francs  ($440) 
Structure  upon  which  to  mount  the  six  dynamo 

machines,  counter-shafting,  etc 8,400  francs  ($1,680) 

Conductors,  material,  and  labor,  for  a  mean  dis- 
tance of  eighty  metres  (262'4  feet)  from  dyna- 
mos to  lamps TOO  francs  ($140) 

Engine  and  boiler  of  ten  horse-power,  with  a  ca- 
pacity of  fifteen  at  need,  including  setting  in 

place 9,800  francs  ($1 ,960) 

Six  Gramme  machines  at  1,500  francs  each 9.000  francs  ($1,800) 

Six  Serrin  regulators  at  450  francs  each 2,700  francs   ($540) 

Five  lanterns,  with  pulleys  and  chains 500  francs   ($100) 

Various  other  items 2,200  francs   ($440) 


Total 35,500  francs  ($7,100) 


The  interest  for  this  amount  and  depreciation,  at  ten  per 
cent,  for  365  days,  and  an  average  ten  hours  daily  operation 


420  APPLICATIONS  OF  THE  ELECTRIC  LIGHT. 

of  the  plant,  represent  '243  franc  (4 '86  cents)  per  lamp  per 
hour. 

The  first  trials  began  with  four  machines  and  four  lamps 
only.   Under  these  conditions,  the  daily  expense  was  as  follows : 

Coal,  400  kilogrammes  (880  pounds)  at 

25  francs  ($5)  per  ton 10  francs  00  centimes  ($2.00) 

Kindling  wood 00  "  15  "  (  .03) 

Mechanic  at  50  centimes  (100)  per  hour,  05  "  00  "  (  1.00) 

Lubricating-oil 00  "  80  "  (  .16) 

Carbon  electrodes,  at  1  franc  50  centimes 

(30  cents)  per  metre  (3'28  feet),  4  lamps 

burning  10  hours  at  10  centimetres  per 

lamp  per  hour 06      "      00         "        (  1.20) 

(These  were  retort  carbons,  9  millimetres 
(595  inch)  thick  and  83  centimetres  (13  inches) 
long.  They  lasted  3J  hours,  waste  included.) 

Gas  for  lighting  the  machine-room 00      "      30        "        (    .06) 

Total  per  day 22  francs  25  centimes  ($4.45) 

Or  per  lamp  per  hour 55.6         "        (     .11) 

Interest  and  depreciation,  as  above 24.3         "        (    .05) 


Cost  of  light  per  lamp  per  hour 79.9  centimes  ($0.16) 

The  lights  are  placed  four  and  a  half  metres  high,  and  the 
lighting  is  sufficient  within  a  radius  of  thirty-five  to  forty 
metres ;  the  lanterns  are  one  metre  in  height  and  *50  metre 
wide ;  to  avoid  the  dazzling,  the  glasses  are  partly  painted 
over  with  zinc-white.  The  lantern  placed  in  the  court  is  pro- 
vided with  double  glasses  to  prevent  breakage  by  cold  or  rain. 
The  ceiling  and  walls  of  the  room  are  whitewashed,  so  as  to 
reflect  the  light. 

This  light  takes  the  place  of  twenty-one  gas-burners,  burn- 
ing 120  litres  (4*2  cubic  feet)  each,  and  the  hand-lamps  which 
the  baggage-agents  had  to  carry  to  find  the  packages,  decipher 
the  addresses,  and  read  the  address  labels.  It  has  reduced 
considerably  the  errors  in  direction  and  delays  resulting  there- 
from, the  damages  caused  by  the  loading  of  goods,  and  the 
consequent  indemnities  of  all  kinds  that  the  company  were 
obliged  to  pay. 

The  weight  of  baggage  moved  during  the  day  per  man  per 
hour  was  850  kilogrammes ;  at  night  it  was  only  530  kilo- 
grammes with  gaslight ;  with  the  electric  light  it  came  to 
680  kilogrammes.  Fifty-five  gas-burners  would  have  been 
required  to  attain  the  same  result. 


INDUSTRIAL  APPLICATIONS. 

If  in  this  example  the  price  of  plant  is  a  little  high,  on 
the  other  hand  fuel  costs  the  Northern  Company  much  less 
than  it  does  individual  consumers.  Assuming  that  a  five-light 
Gramme  machine  was  used,  costing  2,800  francs,  Gramme 
regulators  costing  only  400  francs  each,  and  Carre's  carbons  ; 
and  also  assuming  that  fuel  cost  forty  francs  a  ton,  the  work- 
man sixty  centimes  per  hour,  the  result  attained  is  about 
18,000  francs  for  the  plant,  and  twelve  centimes  for  interest 
and  depreciation.  The  expense  per  hour  comes  to  67*5  cen- 
times, which,  with  the  preceding  figure  of  twelve  centimes, 
gives  79  '5  centimes  for  the  price  per  lamp  per  hour  that  such 
a  system  of  lighting  would  cost  an  ordinary  factory.  It  is 
clear  that  a  special  building  need  not  always  be  constructed, 
and  that  the  motive  power  can  often  be  taken  from  a  more 
powerful  engine  already  driving  other  machines  in  a  factory. 
This  will  diminish  the  expense  greatly. 

The  Paris,  Lyons,  and  Mediterranean  Railroad,  which  in 
September,  1879,  experimented  with  electric  lighting  with  the 
Lontin  Company's  apparatus,  also  decided  to  adopt  this  sys- 
tem for  the  baggage-room  of  the  fast-freight  department. 
But,  instead  of  undertaking  to  produce  the  electricity  itself, 
it  made  an  arrangement  with  the  Lontin  Company  to  furnish 
it  light  at  a  fixed  price  of  fifty  centimes  per  hour  and  per 
lamp.  The  company  has  published  the  following  report  of 
this  lighting  (Fig.  246) : 

The  plant  comprises  eighteen  lamps,  forming  six  series  of 
three  regulators  each,  of  which  six  are  unused  during  such 
times  as  the  service  is  most  restricted,  and  lighted  at  the  mo- 
ment when  it  again  becomes  active.  A  perceptible  economy 
results,  but  its  amount  has  not  yet  been  accurately  deter- 
mined. 

The  cost  of  plant  is  thus  given : 

Steam-engine  of  15  horse-power,  with  capacity 

of  20  at  need 10,000  francs  ($2,000) 

Shafting,  pulleys,  belting,  water-pipes,  etc 1,500  "       (      300) 

Dynamo-electric  machines  (Lontin  system) 15,000  u       (  3,000) 

Cables,  about 7,500  "       (  1,500) 

Nineteen  Mersanne  regulators  (one  for  inter- 
change)      7,600  " 

Lanterns,  suspending  apparatus,  and  other  ac- 
cessories       5,400  " 

Total...    47,000      " 


INDUSTRIAL  APPLICATIONS.  423 

The  interest  and  depreciation  on  this  amount,  at  ten  per 
cent  for  4,000  hours  lighting  per  annum,  come  to  1*175  franc 
per  hour. 

The  items  of  cost  of  running  per  hour  are  : 

Coal  for  the  boilers,  kindling  included,  40 

kilogrammes  (88  pounds),  at  40  francs 

($8)  per  ton 1  franc  60  centimes  ($0.32) 

Carbons  for  the  lamps,  17  metres 1  "55  "  (  .31) 

Oil  and  minor  expenses 0  "  80  "  (  .16) 

Wages  of  two  workmen  for  running  the 

machines,  taking  care  of  and  watching 

the  lamps,  and,  in  winter,  the  wages  of 

a  third  workman  in  the  daytime 1      "50         "         (     .30) 


5      "45  ($1.09) 

Interest  and  depreciation,  as  above 1      *'     17£      "          (     .23  J) 

Total 6      "     62£      "          ($1.32$) 

Or  per  hour  and  per  lamp,  34*6  centimes. 

Something  must  be  added  for  general  expenses  and  main- 
tenance ;  but,  as  the  fuel  is  furnished  by  the  railroad  com- 
pany at  a  lower  price  than  that  given  above,  a  compensating 
saving  will  be  found  in  it.  The  interest  on  the  cost  of  plant 
and  depreciation  represent,  in  this  most  favorable  case,  more 
than  one  fifth  of  the  working  expenses. 

This  system  is  also  used  in  the  Marseilles  passenger  depot 
and  baggage  departments.  The  lighting  of  the  Paris  depot 
has  just  been  extended  to  all  the  departments  of  the  depot ; 
the  number  of  lights  has  been  increased  to  fifty-four,  and  the 
high-power  gas-burners,  which  had  been  experimented  with, 
have  been  abandoned. 

Lighting-plants  of  the  same  character  have  been  estab- 
lished abroad,  always  with  voltaic  arc  lamps,  which  the  height 
of  the  buildings  required  to  be  placed  at  a  sufficient  elevation, 
so  that  a  single  lamp  can  light  from  1,000  to  1,500  square 
metres. 

At  the  King's-Cross  Station  of  the  Great  Northern  Rail- 
road, in  England,  two  covered  sheds,  265  metres  long  by  32 
metres  wide,  and  a  cab-stand  near  the  quay,  are  lighted  by 
fourteen  Crompton  lamps,  supplied  by  five  Burgin  dynamo- 
electric  machines.  The  expenditure  of  motive-power  is 
reckoned  at  twenty-nine  horse-power ;  the  twelve  interior 
lamps  require  a  horse-power  and  a  half  each ;  the  lamps  are 


424  APPLICATIONS   OF  THE  ELECTRIC  LIGHT. 

9|  metres  high,  and  about  30  metres  apart ;  the  three  strong 
lamps,  placed  on  the  outer  facade,  use  three  horse-power 
each ;  they  are  placed  at  a  height  of  20  metres,  and  their 
illuminating  power  is  equal  to  six  hundred  carcels. 

At  St.  Enoch  Station  six  Crompton  lamps  are  used,  sup- 
plied by  six  Gramme  machines. 

The  cost  of  working  is  about  forty  centimes  (eight  cents) 
per  hour  and  per  lamp,  exclusive  of  the  interest  on  the 
investment  and  depreciation,  which  items  we  are  not  in 
possession  of.  We  only  know  that  the  eight-light  Burgin 
machine  costs  about  ten  thousand  francs. 


II. 

For  lighting  large  areas,  then,  the  voltaic  arc  lamps  are 
the  most  economical,  and  in  this  category  must  be  put  open 
yards,  workshops,  and  even  the  quays  and  docks. 

In  the  workshops  of  MM.  Sautter  and  Lemonnier,  which  we 
have  already  cited,  Fig.  232,  three  electric  lights  of  one  hun- 
dred and  fifty  carcels,  supplied  each  one  by  a  Gramme  ma- 
chine, give  a  far  superior  light  to  that  of  the  gas  which  they 
have  replaced.  Each  machine  uses  two  horse-power,  taken 
from  the  steam-engine  of  the  works.  The  consumption  of 
carbons  is  seven  centimetres  per  hour  and  per  lamp. 

M.  Menier  has  had  the  electric  light  since  1875  in  all  his 
factories.  He  uses  fourteen  lamps  of  one  hundred  and  fifty 
carcels.  Each  regulator  is  suspended  by  means  of  a  single 
special  cable  and  windlass,  which  very  happily  solves  the 
problem  of  access  to  the  lamps,  and  permits  them  to  be  placed 
at  the  suitable  height.  The  cable  contains  two  conductors, 
one  annular  and  enveloping  the  other,  with  the  necessary  in- 
sulation ;  this  cable  is,  nevertheless,  sufficiently  pliable  to 
wind  up  without  difficulty  on  the  drum  of  the  windlass. 

The  setting-up  shop  of  the  machine  works  of  MM.  Thomas 
and  Powell,  at  Rouen,  40  by  13  meters,  is  lighted  with  two 
Gramme  machines  and  two  Serrin  regulators,  placed  8  metres 
high,  representing  260  square  metres  per  lamp.  The  plant 
cost  5,000  francs,  and  the  daily  expense  is  '98  franc.  The  mo- 
tive power  expended,  reckoned  at  five  horse-power,  is  derived 
from  a  large  engine,  only  using  1  '50  kilometre  per  horse-power 
per  hour ;  thus  it  only  costs  '18  franc  per  hour. 

It  is  clear  what  services  the  electric  light  can  render  in  the 


FIG.  248. — Farm-work  carried 


by  means  of  the  electric  light. 


INDUSTRIAL  APPLICATIONS.  425 

case  of  out-door  building  operations ;  it  has  been  thus  em- 
ployed from  the  beginning,  even  when  there  was  no  other 
source  than  batteries.  It  was  first  used  at  the  bridge  of 
Notre-Dame.  A  little  later,  the  Northern  Spanish  Railroad 
used,  in  the  GKiadarrama  excavations,  twenty  electric  lights 
during  9,417  hours.  They  were  supplied  by  batteries,  and 
the  expense  per  hour  and  per  lamp  rose  as  high  as  2*90  francs. 
Since  this  epoch,  on  account  of  the  introduction  of  machines, 
it  has  met  with  numerous  applications.  It  was  by  the  assist- 


FIG.  247. — Electric  lighting  of  an  open  space. 

ance  of  the  electric  light  that  the  buildings  of  the  Universal 
Exhibition  of  1878  were  completed  by  the  date  assigned. 

Figs.  247  and  248  show  how  these  applications  are  gener- 
ally arranged. 

The  operations  of  M.  Jeanne  Deslandes  for  the  improve- 
ment of  the  outer  harbor  of  Havre  received  sufficient  light 
from  two  voltaic  arc  lamps  of  five  hundred  carcels  each,  to 
enable  one  hundred  and  fifty  workmen  to  work  without  dif- 
ficulty, and,  more  recently  in  Paris,  the  foundations  of  the 
Credit  Lyonnais  building  were  laid  by  the  light  of  eighteen 
electric  lamps. 


426 


APPLICATIONS   OF  THE  ELECTRIC  LIGHT. 


The  house  of  Sautter  and  Lemonnier  construct  for  this 
out-door  illumination  special  movable  apparatus,  consisting  of 
a  steam  boiler,  a  Brotherhood  engine,  and  a  Gramme  machine. 
The  price  is  six  thousand  five  hundred  francs  for  a  single- 
lamp  apparatus,  and  nine  thousand  francs  for  a  two-lamp  one. 

Other  analogous  systems  have  been  arranged  by  M.  Al- 
baret,  of  Liancourt,  for  the  employment  of  the  electric  light 


FIG.  249.— Electric  lighting  of  the  work  on  the  Kehl  bridge. 

in  agricultural  operations  (Fig.  248).  In  this  case,  a  single 
lamp  may  be  considered  sufficient  for  working  in  a  radius  of 
one  hundred  metres. 

In  January,  1880,  when  the  city  of  Havre  decided  to  intro- 
duce the  electric  light  with  Jablochkoif  candles,  as  described 
in  a  preceding  chapter,  the  chamber  of  commerce  of  Rouen 
carried  on  a  more  complete  series  of  experiments ;  they  de- 
sired to  have  a  light  powerful  enough  to  permit  ships  to  dis- 
charge, load,  and  equip  at  night-time ;  it  also  was  to  facili- 
tate the  watching  at  night  of  the  merchandise  on  the  quays. 

Three  systems  were  tried  simultaneously— the  Jablochkoif 
candles,  the  high  candle-power  lamps  of  Siemens,  and  of  Saut- 
ter and  Lemonnier.  The  "  Bulletin  de  la  Societe  Industrielle  " 


INDUSTRIAL  APPLICATIONS. 


427 


of  Rouen  published,  in  1881,  very  interesting  figures  on  the 
result  of  this  trial. 

Thus,  taking  as  the  minimum  illumination  at  the  limit  of 
the  area  of  action  of  each  lamp  that  given  by  a  carcel  lamp 
at  a  distance  of  three  and  a  half  metres,  and  assuming  the 
lamps  to  be  placed  on  a  single  line  three  thousand  two  hun- 
dred and  fifty  metres  long,  the  following  comparative  figures 
were  obtained : 


i 

SYSTEM. 

1 

ft 

Kadius  of  action 
of  each  lamp. 

METRES. 

Total  surface  lighted 
in  hectares.  (1  hec- 
tare =  2-47  acres.) 

Illuminating  pow- 
er of  a  lamp  in 
carcels 

Total  number  of 
carcels. 

Carcels  per  hectare. 

Consumption  of  car- 
bons per  hour. 

MK.TRE8. 

Total  work  in  ac- 
tual horse-power. 

HORSE-POWER. 

Per  hectare 
lighted,  and 
per  hour. 

Work 
of  the 
motor. 

HORSE- 
POWER 

Carbons 
con- 
sumed. 

METRES. 

Jablochkoff         .           65 

25 

62-50 
65 

16-25 
40-62 
42  '  25 

86 
472 
476-5 

5,590 
12,272 
11,912-5 

344 
302 
281-9 

6-17 
1-33 
2-50 

102-97 

87-75 
112 

6-34 
2-16 
2-65 

0-379 

0-0327 
0-0597 

Sautter  &  Lemonnier.  .  26 
Siemens  25 

If  the  Jablochkoff  candle  be  reckoned  at  1*5  franc  per 
metre,  polar  carbons  at  2  '10  francs  per  metre,  and  a  horse- 
power at  '1  franc  per  hour,  the  following  figures,  per  hour 
and  per  hectare,  lighted  under  the  conditions  given  above, 
are  obtained : 


SYSTEM. 

EXPENSE  OF  CARBONS. 

EXPENSE   OF  POWER. 

Total  ex- 
pense. 
Francs. 

Metres. 

Price  per 
metre. 

Francs. 

Horse- 
power. 

Price  per 
horae-pVr 

Francs. 

Jablochkoff         .    . 

0-3796 
0-0597 
0-0327 

1-50 
2-10 
2-10 

0-5694 
0-1253 
0-0686 

6-34 
2-65 
2  16 

o-io 
o-io 
o-io 

0-634 
0-265 
0-216 

1-2034 
0-3903 
0-2846 

Siemens  

Sautter  &  Lemonnier 

The  end  which  it  was  proposed  to  attain  in  these  experi- 
ments placed  them  under  different  conditions  from  those  of 
ordinary  lighting  of  public  streets,  of  which  we  shall  soon  see 
other  examples. 

III. 

The  Siemens  lamps  used  in  the  Eouen  experiments  are  of 
a  special  large-lamp  model,  called  "  clock-lamps."  We  have 
seen  that,  for  ordinary  lighting,  MM.  Siemens  use  differential 
lamps,  giving  intensities  of  twenty-eight  to  fifty  carcels,  ac- 
cording to  the  number  of  lamps  placed  in  each  circuit.  We 


428 


APPLICATIONS   OF  THE  ELECTRIC  LIGHT. 


give  here  the  figures  which  have  been  obtained  for  the  ex- 
pense of  a  plant  of  this  system  of  lighting  : 

Expense  of  Plant. 


TYPE  OF  MACHINE. 
(Described  in  Book  IV.) 

NUMBER   OF  DIFFERENTIAL   LAMPS. 

4 

6 

8 

10 

12 

16 

20 
Francs. 
3,700 

6,500 
900 

Machines  W3  and  D5 

Francs. 
2,500 

1,300 
225 

Francs. 
2,500 

1,950 
225 

Francs. 
2,500 

2,600 
300 

Francs. 
2,500 

3,250 
300 

Francs. 
3,700 

3,900 
450 

Francs. 
3,700 

5,200 
750 

«        W6    "    D2   

Lamps  each   .            .        300  francs 

Accessories    25       " 

325       " 
f  150  metres 

Cable  at  1*5  franc  per  j              u 
metre 

500       " 
[600       " 

Cost   of    placing    and    incidentals, 
about  5$                 

4,025 
200 

4,675 
230 

5,400 

270 

6,050 
300 

8,050 
400 

9,650 

480 

11,100 
550 

Price  of  Installation...  {^ffip 

4,225 
1,056 

4,905 
817 

5,670 
709 

6,350 
635 

8,450 
704 

10,130 
633 

11,650 

582 

Cost  of  Maintaining  tlie  Light. 


NUMBER  OF  LAMPS. 

4 

6 

8 

10 

12 

16 

20 

Cost  of  installation 

Francs. 
4,225 

538 

Francs. 
4,905 

625 

Francs. 
5,670 

723 

Francs. 
6,350 

810 

Francs. 
8,450 

1,077 

Francs. 
10,130 

1,291 

Francs. 
11,650 

1,485 

Depreciation  for  ten  years,  and  in- 
terest at  5$,  or  a  mean  of  12*75$ 
per  annum  

Depreciation  and  interest  per  hour 
for  600  hours  of  lighting  per  an- 
num   

•89 
•24 

•40 
•30 

•104 
•30 

•60 
•30 

1-20 
•36 

•80 
•30 

1-35 
•42 

1-00 
•30 

1-79 

•48 

J-20 

•50 

215 

•54 

1-60 
•50 

2-47 

•60 
2-00 
•50 

f  4  horse  pow'r 
Coal  for  engine,  215      ' 
kilogrammes  per  |     6      ' 
horse-power  per^    7      ' 
hour,  at  30  francs       8      * 
per  ton  1    9      ' 

[  10     « 
Carbons,  *1  franc  per  lamp  per  hour 
Surveillance  and  oil  

Total  price  per  hour  

1-83 

2-24 

2-66 

3-07 

3-97 

4-79 

5-57 

Price  per  lamp  per  hour...  . 

•457 

•373 

•333 

•307 

•332 

•300 

•278 

INDUSTRIAL  APPLICATIONS.  429 

IV. 

From  the  point  of  view  of  economy,  the  arrangements 
adopted  for  best  utilizing  the  light  of  electric  lamps  are  of 
the  greatest  importance.  One  of  the  great  advantages  of 
powerful  lights  is  that  they  can  be  placed  very  high,  and 
then  not  require  the  use  of  ground  or  opal  globes.  It  is 
enough  in  such  a  case,  to  obtain  the  most  effective  results, 
to  reiiect  toward  the  surface  to  be  lighted  the  rays  sent 
up  above  the  lamp.  Yery  large  flat  reflectors,  or  slightly 
concave  ones,  placed  above  the  lamps,  as  was  done  in  the 
Lyons  Railway  depot  in  1877,  and  as  M.  Jaspar  used  them 
with  much  success  in  the  Electrical  Exhibition  in  Paris, 
are  at  once  the  simplest  and  the  best.  When  it  is  possi- 
ble, as  in  this  last  case,  to  hide  completely  the  luminous  arc, 
using  only  the  reflection,  the  most  satisfactory  results  are 
obtained. 

The  luminous  ceiling,  introduced  in  1877  by  M.  Fon- 
taine, in  one  of  the  halls  of  the  Louvre  stores  in  Paris,  is 
an  interesting  example  of  this  mode  of  lighting  by  reflec- 
tion. The  central  part  of  the  ceiling  was  replaced  by  a 
large,  unsilvered  glass,  above  which  was  placed  the  regu- 
lator and  its  reflector.  This  last  was  formed  of  an  inverted 
frustum  of  a  pyramid,  whose  four  faces  were  coated  with 
tin,  with  a  suitable  arrangement  for  introducing  and  remov- 
ing the  regulator. 

When  the  ceiling  can  be  employed  as  reflector,  there  are 
no  difficulties,  and  M.  Fontaine  has  already  used  it  with  suc- 
cess in  the  thread-mill  of  Mme.  Dieu,  of  Daours  (Somme), 
and  at  M.  Menier's  establishment  at  Noisiel.  But,  when  there 
is  no  ceiling,  as  in  many  workshops,  or  when  the  ceiling  is  of 
glass  and  serves  for  daylight  to  pass  through,  other  means 
must  be  adopted. 

The  flat,  circular  reflectors,  of  which  we  have  spoken,  are 
limited  in  their  dimensions,  and  they  lose  a  great  part  of  the 
rays  sent  up  above  the  lamp.  M.  Boulard  thought  of  sub- 
stituting for  them  a  reflector  with  a  series  of  round  plates, 
whose  width  and  distance  between  the  plates  are  so  graduated 
that  all  the  rays  are  reflected  yet  none  of  them  are  inter- 
cepted. These  plates,  or  blinds  as  they  may  be  called,  only 
descend  to  the  level  of  the  lamp  ;  below  it  they  would  be  use- 
less, because  the  luminous  rays  naturally  distribute  them- 


430  APPLICATIONS   OF  THE  ELECTRIC  LIGHT. 

selves.  It  is,  moreover,  important  for  all  reflectors  to  only 
use  for  reflection  their  lower  surfaces,  which  are  not  ex- 
posed to  obscuration  by  dust.  They  must  not,  either,  be  so 
inclined  as  to  present  dazzling  surfaces,  insupportable  to  the 
eye. 

In  ordinary  lighting,  the  plates  are  of  metal.  Fig.  250 
shows  the  arrangement  of  one  of  these  reflectors  with  a  hori- 
zontal Mersanne  regulator. 

When  it  is  desired  to  avoid  the  line  of  shadow  produced 
at  the  limit  of  action  of  the  reflector  upon  the  neighboring 
surfaces,  such  as  the  facades  of  houses  or  monuments,  the 
plates  are  formed  of  opaline  glass,  and  so  adjusted  as  to  per- 


FIG.  250.— Plate  reflector. 


mit  a  part  of  the  light  to  pass  through.  The  useful  effect  of 
a  city  lantern  thus  provided  has  been  found  far  superior  to 
that  of  all  other  systems  of  diffusion.  The  loss  of  light  does 
not  exceed  ten  per  cent. 


INDUSTEIAL  APPLICATIONS. 


431 


V. 

In  addition  to  these  regulator  systems,  powerful  centers 
of  light  can  be  obtained  with  the  sun  lamp ;  in  this  system, 
more  facility  for  increasing  or  diminishing  the  light  at  will 
is  found,  in  changing  the  intensity  of  the  current  supplying 
them. 

In  estimating  the  cost  of  installation,  allowance  has  only 
to  be  made  for  the  difference  of  cost  between  these  lamps  and 
regulators.  This  difference  may  acquire  considerable  impor- 
tance, because  their  extreme  simplicity  makes  it  possible  to 
obtain  them  at  a  very  low  price.  The  cost  of  the  blocks  and 
of  the  carbons  will  be  slight ;  the  inventors  estimate  it  at  2*5 
centimes  per  hour  for  the  block,  costing  originally  40  centimes 
and  lasting  fifteen  hours.  The  expense  of  carbons  is  reckoned 
at  3  centimes.  These  two  items  give  a  total  of  5*5  centimes 
per  hour  and  per  lamp. 

We  have  no  reports  upon  the  exact  total  expenses  of  ex- 
isting plants,  as  they  have  not  yet  worked  long  enough  ;  but 
we  have  succeeded  in  gathering  the  following  figures  from  a 
report  made  of  a  series  of  experiments  conducted  in  Belgium 
by  MM.  Bede,  Desguin,  Bumont,  and  Rousseau,  engineers 
and  professors  of  physics,  assisted  by  M.  Wauters,  manager 
of  the  Gas  Inspection  Department  of  Brussels : 


Number  of 
lamps. 

Length  of 
blocks  in  milli- 
metres. 

2 

35 

2 

30 

3 

30 

3 

22 

6 

22 

8 

22 

12 

11 

16 

11 

>f 
lilli- 

Intensity  of 
each  lamp  in 

cancels. 

Total  motive 
power  expend- 
ed in  horse- 
power. 

Totul  quantity 
of  light  ob- 
tained in  car- 
eels. 

Number  of 
carcels  per 
horse-power. 

Number  of 
horse-powers 
per  lamp. 

587 

18-0 

1,174 

65 

9-00 

280 

16-5 

560 

34 

8-25 

186 

17-0 

558 

33 

5-65 

256 

12-0 

868 

64 

4-00 

234 

22-8 

1,404 

61 

3-80 

126 

20-9 

1,008 

47 

2-60 

107 

24-7 

1,284 

61 

2-00 

83 

23-8 

1,328 

55 

1-60 

All  the  experiments  were  performed  with  a  self-exciting 
Gramme  machine  of  model  No.  1,  constructed  to  supply  four, 
six,  or  eight  Jablochkoff  candles. 

The  motive  power  was  furnished  by  a  steam-engine  of  25 
nominal  horse  power. 

The  power  was  taken  by  a  Richards  indicator  and  measured 

29 


432  APPLICATIONS   OF  THE   ELECTRIC  LIGHT. 

by  an  Amsler  planimeter.  The  photometric  measurements 
were  taken  with  a  Bunsen  photometer.  We  need  not  recall 
the  particular  qualities  of  this  system,  which  had  much  suc- 
cess at  the  Paris  Exhibition,  where  it  lighted  a  gallery  of  pic- 
tures. 

VI. 

We  have  seen,  in  the  experiments  at  Rouen,  the  Jabloch- 
koff  candles  contrasting  with  the  voltaic  arc  regulators.  Such 
conditions  must  be  disadvantageous  to  them,  because  the  last- 
named  are  much  more  economical  when  the  power  of  the 
burners  can  be  increased,  the  number  diminished,  and  them- 
selves placed  at  a  proper  height.  But  in  proportion  as  these 
favorable  conditions  disappear,  the  economic  difference  be- 
tween the  two  systems  grows  less,  and  often  the  candles  come 
to  be  preferred  on  account  of  their  simplicity. 

The  extra  expense  due  to  them  does  not  only  come  from 
the  increased  motive  power  required  in  the  production  of  cur- 
rents ;  it  comes  also  from  the  inevitable  loss  of  light  from 
the  use  of  globes,  which  they  absolutely  require,  as  they 
must  burn  protected  from  strong  currents  of  air ;  it  must 
be  remembered  that  once  extinguished  the  candle  does  not 
relight. 

This  loss  of  light  can  be  estimated  for  globes  ordinarily 
used,  of  *4  metre  diameter,  at  twenty-five  per  cent  for  Bac- 
carat-glass globes,  at  thirty-three  per  cent  for  roughened 
globes  and  ordinary  light-milky  globes,  and  at  forty-two 
per  cent  for  opal  globes ;  in  calculating  lighting  projects 
with  these  candles,  a  mean  of  forty-one  carcels  for  the  ex- 
posed candle  only  can  be  reckoned  on,  which  reduces  to  thirty 
carcels  for  the  glass  globes,  twenty-seven  for  the  milky 
globes,  and  only  twenty-four  for  ordinary  opal  globes.  On 
the  other  hand,  the  mean  cost  of  establishing  them  hardly 
exceeds  one  thousand  francs  per  light ;  it  varies  again  with 
the  number  of  lamps,  the  extent  of  the  circuit  of  the  conduc- 
tors, and  the  greater  or  less  elegance  of  the  apparatus. 

One  of  the  principal  running  expenses,  the  cost  of  the  can- 
dle itself,  has  diminished  considerably  since  its  beginning,  on 
account  of  the  reduced  price  of  the  carbon  rods,  and  by  the 
successive  improvements  introduced  into  the  manufacture  of 
the  candles  ;  it  has  been  reduced  from  *75  franc  since  July  1, 
1881,  to  *30  franc.  The  length  has  been  slightly  increased, 


INDUSTRIAL  APPLICATIONS.  433 

so  that  their  practical  duration,  which  at  first  was  only  one 
hour  thirty-five  minutes,  can  reach  two  hours  ten  minutes. 
The  motive  power  required  is  an  average  of  one  and  a  half 
horse-power  per  lamp.  It  nevertheless  decreases  as  the  num- 
ber of  lamps  increases,  and  the  engineers  of  the  Metropolitan 
Board  of  Works  in  London,  Sir  Joseph  Bazalgette  and  Mr. 
T.  W.  Keates,  proved  in  1879  that : 

To  produce    5  lights,  T59  horse-power  per  lamp  was  required. 
"  10     "       1-27          u  "  " 

"  15     "        1-03  u  "  " 

"  20     "  -9  "  "  " 

These  figures  express  the  motive  power  in  indicated 
horse-power — that  is  to  say,  the  power  deduced  from  the 
indicator  record.  The  co-efficient  of  reduction  that  they 
employed  to  transfer,  indicated  into  actual  horse-power,  was 
about  *85. 

The  report  of  the  same  engineers  contains  interesting  fig- 
ures relating  to  the  first  installation  of  this  kind  in  London, 
between  Westminster  and  Waterloo  bridges,  upon  a  length  of 
2,150  meters. 

The  cost  of  plant  for  forty  lights  is  estimated  as  follows  : 

One  steam-engine  of  20  horse-power,  nominal, 

including  boiler 12,474  francs  ($2,495) 

Two  Gramme  machines 9,072      "     (  1,814) 

Shafting,  belting,  etc 882      "     (      176) 

Conducting  cables  and  accessories 9,828      "     (1,965.60) 


Total 32,256      "     ($6,451) 

As  the  experiments  only  referred  to  the  first  twenty  lamps, 
the  interest  and  depreciation  were  calculated  for  25, 000  francs 
only,  say  4 '9  centimes  per  hour  per  lamp  for  twenty  lights, 
and  3,600  hours'  service  per  annum. 

The  average  daily  expense  is  : 

Coal   for    boilers,   about    226    kilogrammes   (497 

pounds),  at  21  francs  per  ton 4.70  francs  ($0.94) 

Coal  and  wood  for  kindling 1.20      "      (     .24) 

Oil  and  incidental  expenses  of  the  engine 1.95      "      (     .39) 

Wages  of  mechanics,  firemen,  and  inspectors 16.85      "      (  3.37) 

Salaries  of  assistants '. 12.50      "      (  2.50) 

Total 37.20      "      ($7.40) 

Or  per  lamp  and  per  hour  '338  franc. 


434  APPLICATIONS  OF  THE  ELECTRIC   LIGHT. 

Adding  to  this  the  cost  of  candles  reduced  to  *20  franc  per 
hour  per  lamp  we  find  : 

Daily  expense 338  francs    (6.76  cents) 

Interest  and  depreciation 049      "        (  .98  cents) 

Electric  candles 200      "        (4.00  cents) 


Total 587      "      (11.74  cents) 

The  price  allowed  for  the  candles  in  this  case  seems  less 
than  the  real  expense.  M.  Th.  Levy,  engineer  of  the  Muni- 
cipal Service  of  Paris,  had  demonstrated  in  1878  the  cost  of 
maintenance  per  hour  for  the  sixty- two  lamps  of  the  Avenue 
de  1'Opera  in  the  following  manner : 

Coal  for  boilers 6.64  francs  ($1.828) 

Oil  and  minor  expenses 1.23      "      (    .246) 

Motive  power 3.20      •'       (     .64  ) 

Salary  of  inspectors 3.20      '•       (     .64  ) 

Sixty- two  candles  at  -50  franc 31.00      "      (  6.20  ) 

Total 45.27      "       ($9.054) 

Or  per  lamp  per  hour  '73  franc. 

The  cost  may  have  been  greatly  reduced  since  this  period, 
but  it  is  still  far  above  the  sum  appropriated  by  the  city,  '30 
franc  per  hour  per  lamp  ;  for  this  reason  the  electric  lighting 
has  to  be  stopped  after  midnight  and  the  gas  has  to  be  lighted. 
This  mixed  system  is  only  an  incomplete  solution. 

If  the  city  of  Paris  had  the  honor  of  the  initiative  in  elec- 
tric lighting,  it  must  not  be  forgotten  that  the  trials  were  pur- 
sued in  England,  in  London  notably,  on  a  much  larger  scale. 
Thus,  in  the  beginning  of  1881,  three  districts  were  allotted 
and  conceded,  one  to  the  Brush  Company,  the  second  to  MM. 
Siemens  Brothers,  the  third  to  the  English  Electric  Lighting 
Company. 

The  Brush  Company  support  thirty -three  lamps  on  a  sin- 
gle circuit  of  about  6,600  metres.  The  cables  are  composed  of 
seven  wires  of  1*65  millimetres  diameter,  enveloped  in  India 
rubber  and  with  a  wrapping  of  tarred  ribbon  ;  they  are  placed 
in  cast-iron  pipes  underground.  The  lights  are  five  metres 
high  and  provided  with  reflectors.  The  electricity  is  supplied 
by  two  Brush  machines,  driven  directly  by  a  Brotherhood 
engine  of  thirty-two  horse-power.  The  cost  as  stated  is  about 
18,750  francs  for  the  installation  and  16,500  francs  per  annum 
for  lighting. 


INDUSTRIAL   APPLICATIONS.  435 

MM.  Siemens  use  twenty-eight  ordinary  lamps,  supplied 
by  two  alternate-current  machines,  eighty-six  powerful  lamps 
at  an  elevation  of  twenty- four  metres,  and  each  one  supplied 
by  a  continuous-current  machine.  The  cables  are  also  placed 
in  cast-iron  pipes.  The  cost  for  this  district  is  36,375  francs 
for  the  plant,  and  56,750  for  the  lighting,  per  annum. 

The  third  installation  comprises  ten  very  powerful  lamps, 
supplied  by  two  continuous-current  Gramme  machines.  These 
are  driven  by  a  twenty-five  horse-power  steam-engine.  The 
lamps  of  the  Brockie  system  present  this  peculiarity,  that  the 
movement  of  the  polar  carbons,  instead  of  being  regulated  by 
variations  in  the  intensity  of  the  current,  is  produced  periodi- 
cally by  an  interrupter  of  the  derived  current  actuated  by  the 
motor  of  the  dynamo-electric  machine. 

This  installation  was  ready  for  work  much  later,  the  price 
—33,750  francs  for  the  plant  and  39,500  francs  for  the  light- 
ing— not  having  seemed  enough  to  the  first  company  who  had 
the  allotment. 

In  France  we  have  had  the  very  interesting  trial  which  has 
been  going  on  since  the  National  Fete  of  July  14,  1881,  on  the 
Boulevard  des  Italiens  in  Paris.  Four  lamps  of  Million  (sys- 
tem using  horizontal  carbons,  analogous  to  those  of  M.  de 
Mersanne)  were  suspended  over  the  center  of  the  roadway  of 
the  boulevard  ;  they  were  supplied  by  one  of  M.  de  Meriten's 
machines.  Fig.  251  gives  an  idea  of  this  installation,  which 
seemed  well  adapted  for  lighting  the  boulevards — something 
hard  to  accomplish  because  of  the  trees  bordering  the  road- 
way on  each  side.  Unfortunately,  these  trials  were  of  too 
short  duration.  Finally,  since  November  3,  1881,  the  Place 
du  Carrousel  has  been  lighted  with  fourteen  Mersanne  lamps 
supplied  by  Lontin  machines  ;  twelve  of  these  lamps  are  sus- 
pended from  lamp-posts  placed  on  the  sidewalk  curbs ;  two 
more  intense  lights  are  suspended,  at  a  height  of  twenty  metres, 
from  the  arms  of  a  column  of  iron  lattice-work. 

The  Lyonnaise  Mechanical  Construction  and  Electric  Light- 
ing Company,  which  put  in  this  installation,  also  lights  fifty- 
four  Brush  lamps  in  the  temporary  offices  of  the  Post-Office 
department.  Four  other  Brush  lamps  will  be  lighted  in  the 
Court  of  the  Louvre,  called  the  Court  of  Francis  I,  where  the 
lamp-posts  are  already  erected. 

As  for  the  electric  lighting  of  the  Place  de  la  Bastille,  it 
has  ceased  working  since  the  month  of  February,  1880. 


INDUSTRIAL  APPLICATIONS.  437 

It  is  far  different  in  the  United  States,  where  the  use  of  the 
electric  light  seems  to  have  acquired  a  considerable  develop- 
ment. In  New  York  there  are  six  powerful  companies,  rep- 
resenting together  a  capital  of  thirty  millions  of  francs.  They 
prosper  very  well,  in  spite  of  the  severe  competition  existing 
between  them. 

VII. 

For  the  Werdermann  lamps  we  have  only  the  data  relating 
to  the  installation  effected  in  1879  in  the  Kensington  Museum. 
Two  halls  were  lighted,  each  one  by  four  lamps  of  this  sys- 
tem placed  2*44  metres  above  the  ground,  with  opal  globes. 
They  were  placed  by  fours  in  derivation  upon  the  circuit  of  a 
Gramme  machine,  old  model.  The  motive  power  was  sup- 
plied by  a  gas-engine,  the  Otto  silent,  of  eight  horse-power, 
and  the  gas  used  came  to  eight  and  one  half  cubic  metres 
(297^  cubic  feet)  per  hour. 

In  an  experiment  made  in  Paris  in  1879  a  special  Gramme 
machine,  driven  by  a  six  horse-power  gas-engine,  was  found 
capable  of  supplying  ten  Werdermann  lamps  of  fifteen  carcels, 
or  twelve  lamps  of  twelve  carcels.  The  carbons  were  four  and 
one  half  millimetres  in  diameter,  and  the  consumption  came 
to  ten  centimetres  (four  inches)  per  hour  for  each  lamp. 

We  do  not  know  the  exact  running  expenses  of  the  Wer- 
dermann-Reynier-Napoli  lamps — we  only  know  that  the  twen- 
ty-four lamps  of  this  system  that  worked  at  the  Electrical 
Exhibition  in  Paris  were  supplied  by  a  self-exciting  twenty- 
light  Gramme  machine,  requiring  about  twenty  horse-power. 
The  expense  per  hour  and  per  lamp  may  be  put  at  about  '30 
franc.  We  are  in  possession  of  somewhat  more  exact  figures 
relative  to  the  lighting  of  the  bleachery  of  M.  P.  Duchesne- 
Fouret,  in  the  Valley  of  Auge,  the  work  being  executed  by 
M.  Reynier,  and  the  figures  established  by  M.  E.  Dupuy,  en- 
gineer and  director  of  this  establishment. 

This  lighting  comprises  eleven  Reynier  lamps,  distributed 
as  follows  : 

Four  in  the  soaping  and  washing  rooms.  46*20  x  16-60  metres  =  766'92  sq.  metres. 

One  in  the  wringing-room 19-70  x  16'60 

Two  in  the  first  drying-room 66-20  x  11-50 


Two  in  the  second  drying-room 66-20  x  11-50 

One  in  the  engine-room 10'70  x    6-60 

One  in  the  boiler-room. . .  .   11-50  x    6-80 


=  327-02 
=  761-30 
=  761-30 
=  69-62 
=  78-20 


438  APPLICATIONS  OF  THE  ELECTRIC  LIGHT. 

The  expense  of  installation  comprises  : 

One  Gramme  machine  (factory  type) 1,500  francs  ($300) 

Eleven  Eeynier  lamps 1,100      "      (  220) 


Eleven  Reynier  automatic  lighters 275 


One  interrupter 30  (  6) 

One  galvanometer 30  fc  (  6) 

Five  two-way  switches,  special  model 150  '  (  30) 

Twenty  white-glass  globes ; . .  40  '  (  8) 

Ten  tin  reflectors 50  '  (  10) 

Two  hundred  and  eighty -five  metres  of  cables  and 

different  wires 240  u  (  48) 


(    55) 


Total 3,415      "       ($683) 

The  interest  and  depreciation  on  which  amount,  at  the  rate  of 
ten  per  cent  and  for  seven  hundred  hours  of  lighting,  come 
to  *488  franc  per  hour. 

The  Gramme  machine  makes  1,275  revolutions  per  minute  ; 
the  motive  power  taken  from  the  factory  engine  is  reckoned 
at  three  horse-powers,  which  seems  rather  too  little.  The  run- 
ning cost  per  hour  is  : 

Carbon  rod  for  the  lamps  at  the  rate  of  17  centi- 
metres per  hour  per  lamp,  1-87  metre,  at  -35 
franc 0.655  francs  ($0.131  ) 

Motive  power,  3  horse-power,  at  0  06  franc. ...  0.180      "      (    .036  ) 

Total 0.835      "      ($0.167) 

Interest  and  depreciation 0.488      "       (     .0976) 


Together 1.323      "       ($0.2646) 

Or  about  '12  franc  per  hour  per  lamp,  whose  photometric 
value  is  equal  to  eight  to  twelve  carcels.  It  is  a  very  advan- 
tageous result  for  a  factory  obliged  to  manufacture  its  own 
lighting  gas. 

This  class  of  applications  will  certainly  multiply,  if  all  the 
companies  which  exploit  the  different  lighting  systems  will 
publish  the  necessary  data  to  establish  comparative  exact  and 
complete  figures. 

VIII. 

We  have  not  believed  it  necessary,  as  it  often  is  thought, 
to  compare  the  economic  results  of  electric  lighting  with  those 
of  gas  lighting.  In  general,  when  it  is  decided  to  use  electric 
light,  it  is  for  the  object  of  obtaining  a  sum  total  of  light  far 
greater  than  that  which  existed  before,  and  which  proved  in- 


INDUSTRIAL  APPLICATIONS.  439 

sufficient.  For  the  comparison  to  be  just,  it  must  be  made 
with  the  gas  necessary  for  the  production  of  the  same  de- 
gree of  light,  and  in  this  case  the  advantage  is  with  electricity. 

It  is  far  otherwise  with  incandescent  lighting  by  the  Edi- 
son, Swan,  and  other  systems,  whose  light  has  almost  the 
actual  value  of  our  gas-jets.  In  spite  of  their  superiority, 
the  small  electric  lights  can  not  hope  to  be  adopted  unless 
they  cost  no  more  ;  Edison  hopes  to  reach  this  point  with  the 
installation  he  is  preparing  in  New  York,  and  all  the  plans  of 
which  he  has  exhibited  in  Paris  ;  it  is  enough  in  fact  to  dis- 
tribute the  cost  of  plant  and  exploitation  among  a  considera- 
ble number  of  lamps  and  hours  of  lighting.  There  is  nothing 
impracticable  in  this.  Allowing  for  an  installation  of  only 
five  hundred  horse-power,  supplying  ten  thousand  lamps  *  in  a 
net- work  of  twenty -five  or  thirty  kilometres,  an  annual  rev- 
enue of  450,000  francs  is  reached  on  the  basis  of  a  price  of 
three  centimes  per  hour  and  per  lamp,  and  for  1,500  hours 
lighting  per  annum.  Estimating  this  first  installation  at 
2,000,000  of  francs  or  100,000  francs  interest  per  annum,  and 
the  motive  power  at  30,000  francs,  there  is  left  for  other  ex- 
penses and  profits  320,000  francs.  We  have  already  seen 
that  this  price  of  three  centimes  is  lower  than  the  net 
cost. 

But  if,  instead  of  confining  the  work  to  lighting,  electricity 
is  furnished,  as  M.  Marcel  Deprez  suggests,  at  once  for  light 
and  for  power  at  home,  the  number  of  hours  of  activity  may 
exceed  four  thousand  per  annum.  Success  does  not  seem 
doubtful. 

It  must  not  be  concluded  from  this  that  the  use  of  the 
electric  light  is  dependent  on  the  formation  of  such  immense 
plants.  It  is  already  utilized  with  advantage  on  the  condition 
of  producing  at  the  lowest  possible  price  the  power  required. 
This  is  difficult  because,  as  we  know,  the  smaller  the  power 
the  greater  the  relative  cost  of  producing  it. 

Up  to  the  present  time,  for  electric  lighting,  portable  en- 
gines or  those  of  an  analogous  type  have  generally  been  used, 
and  it  is  on  the  work  of  such  engines  that  the  cost  of  elec- 
tricity must  be  calculated. 

In  a  conference  held  at  the  Congress  of  Electricians  in 
1881,  Professor  Ayrton  recalled  that,  in  a  recent  exhibition 

*  [In  the  first  Edison  district  in  New  York,  six  lamps  are  maintained  per 
indicated  horse-power.  This  figure  is  therefore  much  too  high.] 


440  APPLICATIONS   OF   THE  ELECTRIC  LIGHT. 

in  England,  where  several  of  the  best  machines  of  this  type 
were  running,  the  consumption  of  coal  ran  as  high  as  two  kilo- 
grammes—  exactly  1*800  kilogrammes  —  (four  pounds)  per 
horse-power  per  hour. 

As  all  this  took  place  at  an  exhibition,  where  the  cost  was 
to  be  (determined,  nothing  was  neglected  to  obtain  the  most 
favorable  conditions  ;  the  fires  were  managed  by  experienced 
firemen,  the  boilers  were  new  and  clean.  This  does  not  rep- 
resent the  daily  condition  of  such  things  in  ordinary  work, 
where  2*5  to  3  kilogrammes  (5J  to  6 '6  pounds)  represent  more 
nearly  the  usual  consumption,  especially  when  the  boilers 
have  worked  several  months  ;  it  is  a  return  of  only  one  thir- 
tieth of  the  calorific  power  of  the  carbon. 

It  is  hardly  necessary  to  add  that  all  those  who  employ 
portable  engines  in  different  localities  agree  that  the  practical 
consumption  is  much  higher,  that  it  goes  up  to  five  or  six 
kilogrammes  per  horse-power  per  hour,  and  even  higher  in 
many  operations  where  the  wasting  of  the  coal  is  unavoid- 
able. 

It  becomes  absolutely  necessary  to  find  a  motor  that  is 
more  economical  to  drive  the  dynamo-electric  machine  if  the 
cost  of  electricity  is  to  be  diminished.  We  have  also  the  hot- 
air  engine,  whose  use  in  English  light-houses  we  have  alluded 
to.  Its  return  of  power  is  governed  by  the  same  law  as  that 
of  steam-engines — the  fall  of  temperature  during  its  work 
upon  the  piston.  For  it,  also,  the  initial  temperature  must  be 
increased  to  obtain  good  results,  because  the  pressure  of  hot 
air  increases  more  slowly  than  that  of  steam.  It  can  be  raised, 
then,  without  danger,  to  temperatures  where  the  latter  would 
be  capable  of  breaking  all  inclosures. 

Unfortunately,  this  advantage  is  accompanied  with  a  trou- 
ble that  quite  annuls  it ;  lubricating  oils  burn  very  easily,  and 
the  bearings  soon  begin  to  rub.  These  engines  are  also  very 
large  and  heavy  ;  the  slowness  of  their  motions  does  not  cor- 
respond to  the  high  speeds  of  dynamo-electric  machines,  and 
brings  on  complicated  problems  of  transmission. 

The  gas-engine  remains,  in  which  the  power  is  produced 
by  the  explosion  of  a  mixture  of  air  and  gas  introduced  into 
the  interior  of  a  cylinder  at  each  movement  of  the  piston. 

There  is  a  great  difference  between  the  hot-air  engine  and 
the  gas-engine.  It  is  that  in  this  last  class  of  motors  the  ele- 
vation of  heat  is  produced  within  the  interior  of  the  cylinder, 


INDUSTRIAL  APPLICATIONS.  441 

so  that,  in  spite  of  the  high  temperature  of  the  gas,  the  cylin- 
der and  piston  can  be  cooled,  and  the  lubricators  kept  from 
drying,  by  means  of  a  current  of  cold  water.  This  useful 
cooling  is  impossible  in  the  hot-air  engine,  the  air  being 
heated  outside  of  the  cylinder.  Again  the  mixture  of  air  and 
gas  enters  the  cylinder  at  a  low  temperature.  After  the  ex- 
plosion there  is  a  sudden  lowering  of  the  high  temperature 
developed,  because  the  piston  moves  before  the  gases  have 
time  to  communicate  much  of  their  heat  to  the  cylinder  or 
piston. 

Superheated  steam  can  not,  either,  be  employed  without  re- 
course to  apparatus  of  extreme  strength ;  account  must  also 
be  taken  of  the  great  loss  of  heat,  in  the  passage  of  this  highly- 
heated  vapor  through  the  pipes  and  distributing  apparatus, 
which  would  also  be  rapidly  deteriorated  by  an  excessive 
heat.  It  is  clear,  then,  that  with  a  gas-motor  the  high  tem- 
perature necessary  for  an  economical  result  can  be  used  with- 
out encountering  the  practical  difficulties  which  have  pre- 
vented the  use  of  steam  or  hot  air  under  the  same  conditions. 

In  actual  steam-engines  the  steam  hardly  ever  exceeds  180° 
C.  at  its  entrance  into  the  cylinder,  and  the  fall  of  tempera- 
ture during  the  period  of  work  may  reach  120°  C.,  which  will 
furnish,  according  to  thermo-dynamic  laws,  a  theoretical  re- 
turn of  twenty  per  cent,  or  one  fifth.  *  In  a  gas-engine  the 
initial  temperature  at  the  moment  of  explosion  is  estimated 
at  2,500°  C.,  and  it  falls  to  about  300°  C.  when  the  piston  has 
completed  its  movement,  which  gives  a  fall  of  temperature  of 
2,200°  C.,  corresponding  to  a  theoretical  return  of  three  quar- 
ters, or  of  seventy-five  per  cent  instead  of  twenty  per  cent.f 

Thus  the  gas-engine  works  under  much  more  favorable 
conditions  than  a  steam  or  hot-air  engine — that  is  to  say,  it 
transforms  into  mechanical  work  a  much  greater  quantity  of 
the  heat  produced.  But  it  does  not  follow  from  this  that  it 
works  more  cheaply.  This  depends  on  the  price  of  combus- 

*  [With  these  extremes  of  temperature  this  would  be  26'5  per  cent,  nearly, 

T  -  T'      (180  +  273)  -  (60  +  273)       120 

as  follows :  Efficiency  = =  v —          — — — =  —  =  -265.1 

T  180  +  273  453 

t  [These  figures  are  much  too  high.     Mr.  Dugald  Clerk  gives  1537°  0.  as  the 
maximum  temperature,  and  648°  0.  as  the  temperature  of  exhaust  in  the  most 
economical  type  of  the  gas-engine.     This  would  make  the  theoretical  efficiency 
(1537 +  273) -(648 +  273)  _    889  _  ^ 

1537  +  273~"  =   1810"        -1 


442  APPLICATIONS  OF  THE  ELECTRIC  LIGHT. 

tibles  used,  and  on  the  other  greatly  varying  items  of  cost 
necessarily  incurred  in  the  running  of  any  machine. 

To  make  the  comparison  with  some  approach  to  exactness, 
Professor  Ayrton  has  arranged  detailed  tables  of  the  expenses 
of  all  sorts  required  by  two  motors  of  thirty  horse-power,  one 
a  steam-engine  of  the  portable  type,  the  other  a  gas-engine  of 
the  Otto  type,  running  three  hundred  days,  ten  hours  a  day— 
that  is  to  say,  for  three  thousand  hours  of  effective  work. 
The  final  result  came  to  9,500  francs  for  the  steam-engine,  and 
11,100  francs,  or  1,600  francs  more,  for  the  gas-engine.  It  is 
a  difference  of  sixteen  per  cent.  It  must  be  stated  here  that 
in  the  calculation  gas  is  charged  at  fifteen  centimes  a  cubic 
metre  (eighty-six  cents  per  thousand  feet),  which  is  one  half 
the  price  charged  in  Paris  to  small  consumers.  If  it  be  cal- 
culated on  the  basis  of  its  selling  price,  the  total  expense  of 
the  gas-engine  will  exceed  21,500  francs — that  is  to  say,  more 
than  double  that  of  the  steam-engine  doing  the  same  work. 

Such  a  result  does  not  seem  encouraging.  But  coal  to-day 
is  manufactured  for  the  production  of  light,  and  not  of  heat ; 
it  must,  to  be  adapted  for  this  purpose,  undergo  costly  purify- 
ing operations,  which  diminish  rather  than  increase  its  calorific 
power.  When  it  is  used  for  heating  it  is  turned  aside  entirely 
from  its  original  destination,  and  it  should  occasion  no  sur- 
prise if  bad  results  are  obtained. 

In  spite  of  this  feature,  the  enormous  calorific  power  of 
gas  is  so  inefficiently  utilized  in  the  production  of  ordinary 
lights  that  there  is  an  advantage  in  transforming  it  into  motive 
power,  and  in  converting  this  into  electricity  and  into  light. 
A  cubic  metre  of  gas  burned  in  ordinary  burners  does  not 
give  over  eight  or  nine  carcels  of  light ;  it  is  true  that  here  we 
experience  the  bad  economy  of  division,  because,  with  Siemens 
regenerating  burners,  a  cubic  metre  of  gas  can  give  as  much 
as  'thirty-five  carcels.  Used  in  a  gas-engine,  it  represents  a 
horse-power,  that  is  to  say,  an  average  light  of  one  hundred 
to  one  hundred  and  twenty  carcels ;  but  this  advantage  dis- 
appears if,  in  its  turn,  the  electricity  be  divided  into  small 
lights — and,  with  incandescent  lamps,  scarcely  twice  the  light 
produced  by  direct  combustion  in  burners  will  be  obtained. 

On  the  other  hand,  gas-engines  are  without  danger ;  they 
can  be  placed  anywhere  without  permission  from  the  authori- 
ties ;  no  special  workmen  are  required  to  run  them ;  they 
work  without  noise ;  the  expenditure  of  gas  governs  itself 


INDUSTRIAL  APPLICATIONS.  443 

automatically  in  proportion  to  the  work  done,  and  ceases  as 
soon  as  the  work  ceases  ;  all  that  has  to  be  added  to  the  ex- 
pense are  the  items  of  oiling  and  of  about  fifty  litres  of  water 
per  horse-power  per  hour  to  be  used  in  cooling  the  cylinder.* 
These  machines  are  an  excellent  resource  whenever  more 
powerful  lights  or  more  beautiful  illumination  is  required. 
They  are  made  of  all  sizes,  and  at  the  Electrical  Exhibition 
in  Paris  they  contributed  largely  to  the  production  of  the 
motive  power  necessary  for  the  evening  illumination.  They 
represented  one  hundred  and  fifty-two  horse-powers  distrib- 
uted in  the  following  manner : 

One  engine  of  fifty  horse-power,  driving  sixteen  Gramme 
machines,  factory  type,  divided  into  two  groups. 

One  engine  of  twenty -five  horse-power,  driving  a  Kreme- 
netzki  machine,  and  the  six  Gramme  machines  of  the  Gravier 
distribution  system. 

One  engine  of  twenty -five  horse -power,  driving  seven 
Gramme  machines,  factory  type,  and  one  two-light  Gramme 
machine,  of  the  Sautter-Lemonnier  Company. 

One  engine  of  twenty  horse-power,  driving  the  Schuckert 
(six  lights)  and  Gulcher  (six  to  twelve  lights)  machines. 

One  engine  of  twelve  horse-power,  driving  one  Gramme 
machine,  factory  type,  and  one  Gramme  self-exciter  for  eight 
Jablochkoff  candles. 

One  engine  of  eight  horse-power,  driving  one  Gramme  elec- 
troplating machine  (Christofle),  two  Gramme  machines,  fac- 
tory type  (two  light),  and  one  Gramme  self-exciter  for  four 
Jablochkoff  candles. 

One  engine  of  eight  horse-power,  driving  two  Gramme  ma- 
chines, supplying  the  two  lights  in  the  green-house. 

One  engine  of  four  horse-power,  driving  the  two  Gramme 
machines  on  M.  Deprez's  circuit. 

The  machines  used  for  lighting  the  green-house  (showing 
the  influence  of  the  light  upon  vegetation)  worked  night  and 
day  without  cessation  during  the  whole  time  of  the  Exhibi- 
tion. 

The  speed  of  these  machines  was  one  hundred  and  forty 
revolutions  for  the  five  first,  and  one  hundred  and  sixty  revo- 
lutions for  the  others. 

To  reduce  the  expense  of  gas-engines  it  has  even  been  pro- 

*  [No  expenditure  is  necessary  on  this  account,  as  the  same  water  is  used 
over  and  over  again.] 


444:  APPLICATIONS   OF  THE  ELECTRIC  LIGHT. 

posed  to  manufacture  a  special  gas,  and  Mr.  E.  Dowson,  of 
London,  showed  at  the  Electrical  Exhibition  a  new  apparatus 
producing  very  cheaply  excellent  gas  for  the  motors. 

Using  just  such  means  as  those' alluded  to  above,  for  a 
Dowson  gas-motor  of  thirty  horse-power,  running  three  hun- 
dred days,  during  a  period  of  ten  hours  each  day,  Professor 
Ayrton  reached  a  total  cost  of  5,240  francs.  This  new  engine, 
then,  will  cost  forty -five  per  cent  less  than  a  steam-engine  and 
fifty-three  per  cent  less  than  an  ordinary  gas-engine  supplied 
by  illuminating  gas  at  a  rate  of  fifteen  centimes — that  is  to 
say,  one  half  the  cost  of  Paris  gas. 

Unfortunately,  the  establishment  under  our  public  streets 
of  a  new  system  of  gas-mains  is  at  present  almost  impossible 
of  realization,  and  could  not  pay  except  by  a  greater  devel- 
opment of  the  uses  of  the  new  gas  than  could  be  counted 
upon,  especially  with  the  resources  now  offered  us  by  elec- 
tricity in  the  distribution  of  motive  power. 

This  is,  moreover,  much  more  advantageous,  because  it 
admits  of  a  division  which  can  never  be  attained  with  other 
motors.  But  nothing  will  prevent  the  realization  of  the  econ- 
omy presented  by  the  use  of  the  Dowson  gas,  in  employing  for 
the  production  of  electricity  powerful  gas-engines  in  place  of 
steam-engines.  This  new  way,  opened  up  for  the  utilization 
of  combustibles,  may  bring  about  an  industrial  revolution  in 
the  production  of  motive  power. 


IX. 

Some  have  thought  of  developing  the  use  of  vacuum  incan- 
descent burners,  with  accumulators  that  could  be  charged 
during  the  daytime,  either  by  Eeynier  or  Thompson  batteries, 
or  by  a  dynamo-electric  machine  driven  by  a  gas-engine.  But, 
besides  the  fact  that  the  plant  would  be  too  complicated  for 
an  unimportant  lighting,  we  do  not  know  yet  whether  the  in- 
candescent lamps  of  different  systems  which  were  seen  at  the 
Electrical  Exhibition  can  be  procured,  and,  if  they  could  be 
found,  they  would  cost  too  much  ;  they  speak  of  twenty-five 
francs  per  Swan  lamp  for  the  first  purchase,  and  12*50  francs 
for  the  lamps  that  replace  the  first,  whose  duration  is  only 
guaranteed  to  be  three  hundred  hours  burning.  It  would 
probably  be  just  as  difficult  to  obtain  improved  accumulators. 
All  this  has  not  passed  the  experimental  stage,  although  a 


INDUSTRIAL  APPLICATIONS.  445 

very  interesting  application  of  it  has  been  recently  made  in 
England.  On  the  London  and  Brighton  line  a  car  is  lighted 
by  twelve  Swan  lamps  supplied  by  thirty-two  Faure  accumu- 
lators. These  same  lamps  are  also  on  trial  in  lighting  the 
interior  of  armored  vessels,  and  in  mine  galleries. 

Assuming  an  approximate  estimate  for  the  installation  of 
fifty  of  these  lamps,  at  a  probable  cost  of  five  francs  per  lamp 
(Edison  system),  the  lighting  will  come  to  the  following :  For 
five  hundred  hours  per  annum,  8  '2  centimes  per  hour  and  per 
lamp  ;  for  fifteen  hundred  hours,  a  term  which  may  be  ap- 
plied to  domestic  lighting,  1-8  centime  ;  for  four  thousand 
hours'  lighting,  the  cost  descends  to  1  *4  centime. 

While  waiting  for  industrial  lighting  to  be  instituted,  very 
interesting  applications  have  been  made  in  England,  which 
show  well  how  the  electric  light  can  be  made  use  of  in  domes- 
tic economy. 

The  late  Mr.  Spottiswoode,  president  of  the  Royal  Society 
of  London,  used,  for  his  country-house  and  laboratory  at 
Coombe  Bank,  a  large  magneto-electric  machine  of  M.  de 
Meritens,  two  Gramme  .machines,  factory  type,  one  small 
continuous-current  Siemens  machine,  and  one  large  Burgin 
machine.  Besides  the  experiments  for  which  they  are  des- 
tined, these  machines  give  a  very  remarkable  illumination, 
which  comprises  twelve  Jablochkoff  candles,  four  powerful 
Crompton  lamps,  and  ninety  Swan  incandescent  lamps ;  of 
these  last,  thirty  light  the  grand  saloon,  twenty  are  in  the 
dining-hall,  and  the  rest  are  distributed  through  the  other 
parts  of  the  chateau. 

Elsewhere,  Sir  W.  Gr.  Armstrong  uses  the  incandescent 
light  for  lighting  his  residence  in  the  country,  and  that  almost 
without  expense,  the  motive  power  coming  from  a  neighbor- 
ing water-fall.  A  six  horse-power  turbine  drives  a  Siemens 
dynamo-electric  machine  ;  the  distance  of  the  turbine  from 
the  house  is  about  four  and  a  half  kilometres,  the  conductors 
are  formed  of  copper  wire  seven  millimetres  thick.  The  num- 
ber of  Swan  lamps  is  forty-five,  but,  as  a  rule,  only  thirty- 
seven  are  lighted  at  the  same  time. 

The  library,  which  is  ten  metres  by  six,  is  perfectly  lighted 
by  eight  lamps  ;  the  dining-room,  also  by  eight  lamps,  six  of 
which  form  a  lustre  over  the  table ;  the  two  others  are  in 
brackets.  A  picture-gallery,  serving  as  a  study,  is  lighted  by 
twelve  suspended  lamps,  to  which  are  added  eight  others 


446  APPLICATIONS  OF  THE  ELECTRIC  LIGHT. 

when  the  dining-room  is  darkened  ;  the  gallery  is  well  lighted 
by  the  twelve  lamps,  but,  with  all  twenty  lamps  in  operation, 
the  pictures  show  to  as  much  advantage  as  in  daylight. 

The  other  lamps  are  distributed  through  the  other  rooms 
of  the  house. 

Each  lamp  is  estimated  at  twenty-five  candles,  so  that  the 
six  horse-power  gives  a  total  light  of  about  two  hundred  and 
twenty-five  candles. 

In  conclusion,  it  must  be  said  that  the  electric  light  has 
won  for  itself  an  important  position  among  the  resources  of 
our  civilization ;  its  defects  will  vanish  one  by  one,  and  each 
new  improvement  is  followed  immediately  by  numerous  ap- 
plications ;  its  qualities  were  demonstrated  at  the  Exhibition 
of  1881,  so  as  to  convince  most  of  its  adversaries.  Its  general 
use  is  only  a  question  of  time  ;  it  always  was  the  same  with 
inventions  that  disarrange  our  habits,  and  force  us  to  learn 
new  things.  It  is  probable  that  our  grandchildren  will  pity 
us  who  depended  on  gas  and  steam-engines,  as  we  pity  our 
ancestors  who  only  had  candles  and  stage-coaches. 


INDEX. 


Accumulation,  principle  of  mutual,  in 

dynamos,  239. 
Accumulator,  202. 

use  of,  in  electric  lighting,  444. 
Air-pump,  mercury,  Geisler,  159. 

Sprengel,  161. 

Alliance  magneto-electric  machine,  233. 
Amerique,  steamer,  electric-lighting  ar- 
rangements of,  401. 
Ampere's  discovery  of  mutual  action  of 

currents,  211. 
Ampere,  the,  44. 
Apparatus,  automatic  safety,  90. 
Apparitions,  productions  of.  in  the  thea- 
tre by  means  of  the  electric  light, 
414 
Arago's  discovery  of  the  electro-magnet, 

211. 

Archereau's  arc  lamp,  67. 
Arc  lamp.     (See  Lamp,  arc.) 
Arc  light,  experiments  of  Lacassagne  and 

Thiers,  23. 

first  use  in  England  by  Staite,  22. 
Arc,  voltaic,  counter  electro-motive  force 

of  the,  35. 

discovery  of,  by  Davy,  21. 
effect  of  greatly  enlarging  one  carbon 

pole,  127. 
effect  of  displacement  of  the  carbons  out 

of  line,  56. 
experiments  in  lighting  with  the,  by 

Deleuil  and  Archereau,  22. 
experiments  of  Masson  and  Matteucci, 

22. 

form  of  the  carbon -poles  with  con- 
tinuous current,  35. 
with  alternating  current,  35. 
refractory  material  in  the,  experiments 
of  M.  Leroux,  138. 


Arc,  voltaic,  to  what  the  light  of  the,  is 

due,  34 

Armature,  Brush   dynamo-electric    ma- 
chine, 279,  283. 

Biirgin  dynamo-electric  machine,  289. 

De  Meritens  alternating-current   ma- 
chine, 292. 

De  Meritens  continuous-current    ma- 
chine, 295. 

Edison  dynamo-electric  machine,  273. 

Ferranti  alternating-current  machine, 
263. 

Gordon   alternating-current    machine, 
264. 

Gramme  alternating-current  machine, 
249. 

Gramme  continuous-current  machine, 
242. 

Lontin    alternating-current    machine, 
288. 

Lontin  dynamo-electric  machine,  287. 

Maxim  dynamo-electric  machine,  267. 

Niaudet  dynamo-electric  machine,  287. 

Siemens  alternating-current  machine, 
261. 

Siemens  continuous-current  machine, 
257. 

Siemens,  236. 

Weston  dynamo-electric  machine,  266. 

Wood  dynamo-electric  machine,  253. 
Armatures,  classification  of,  with  refer- 
ence to  their  form,  225. 

induction  in  polar,  230. 

induction  in  ring,  228. 
Armstrong's  lighting  of  his  residence,  445. 
Artificial  carbons.    (See  Carbons,  artifi- 
cial.) 

Automatic  lighter,  Reynier,  132. 
Ayrton  and  Perry's  work-meter,  369. 


448 


INDEX. 


Battery,  Bunsen,  200. 

Carre,  201. 

constant,  199. 

Daniell,  199. 

Grove,  200. 

hydro-electric,  196. 

pyro-electric,  of  Becquerel,  210. 

pyro-electric,  of  Jablochkoff,  210. 

Reynier,  201. 

secondary  or  storage,  202. 
Battery,  storage,  Brush,  206. 

De  Meritens,  205. 

Faure,  204.    . 

formation  of  the  plates  of,  203. 

Kabath,  206. 

Plante,  203. 

Sellon-Volckmar,  205. 

Sutton,  206. 

tests  of,  206. 

Thomson  and  Houston,  205. 
Battery,  thermo-electric,  207. 

thermo-electric,  Clamond,  208. 

Tomasi,  201. 

Battery,  voltaic,  invention  of,  20. 
Becquerel  pyro-electric  battery,  210. 
Bernstein  incandescent  lamp,  181. 
Boulard  plate  reflectors,  429. 
Boxes,  junction-,  Edison,  for  underground 

conductors,  330. 

Box,  junction-,  for  underground  conduct- 
ors, used  by  the  Jablochkoff  company, 

323. 
Boys  current-meter,  366. 

work-meter,  368. 
Bridge,  Wheatstone,  182. 
Brush  arc  lamp,  82. 

automatic  cut-out,  96. 

commutator,  281,  283. 

dynamo-electric  machine,  279. 

dynamo,  measurement  of,  by  Paris  com- 
mittee, 307. 

regulation  of  dynamo  for  arc  lighting, 
354. 

storage-battery,  206. 
Brushes,  displacement  of  dynamo,  reason 

for,  231. 

Gravier's  plumbago  commutator,  297. 
Bunsen  battery,  200. 
Blirgin  arc  lamp,  65. 
Blirgin  dynamo-electric  machine,  289. 
dynamo,  measurement  of,  by  Paris  com- 
mittee, 307. 


Calorie,  the,  42. 

Canalization  of  Edison,  329. 

Candle,  electric,  cost  of  the  Jablochkoff, 

427,432. 
Debrun,  114. 

Candle,  electric,  Jablochkoff,  98. 
construction  of,  101. 
installation    of    the,  for  lighting  the 

port  of  Havre,  317. 
office  of    the  insulating  material  in, 

138. 
Candle,  electric,  Jam  in,  112. 

Wilde,  110. 

Candle,  first  factory  for  the   manufact- 
ure of  stearine,  5. 

Candle,  introduction  of  the  tallow,  3. 
star,  origin  of  the  name,  5. 
stearine,  manufacture  of.  by  Chevreul 

and  Gay-Lussac,  4. 
stearine,  manufacture   of,  by  Camba- 

ceres,  4. 
stearine,  manufacture  of,  by  MM.  de 

Milly  and  Matard,  4. 
Capacity,  C.  G.  S.  unit  of,  44. 

practical  unit  of,  45. 

Carbons,  artificial,  composition  of,  47-51. 
Archereau,  48. 
Bunsen,  47. 

E.  Carre,  49. 

F.  Carre,  49. 
Gaudoin,  49. 
Jacquelain,  48. 
Lacassagne  and  Thiers,  48. 
Napoli,  49. 

Siemens,  49. 

Staite  and  Edwards,  47. 

use  of  the  draw-plate  in  the  manufact- 
ure of,  48. 

Carbons,  burning  qualities  of  bare,  cop- 
per, and  nickel  plated,  54. 

compound,  of  M.  Carre,  54. 

for  the  arc  lamp,  46. 

gas-retort,  46. 

gas-retort,  objection  to,  46. 

light  obtained  with  those  of  different 
makers,  51. 

metal-covered,  54. 

position  of,  for  throwing  the  light  in 
one  direction,  56. 

used  by  Davy,  46. 
Carre's  arc  lamp,  71. 

battery,  201. 


INDEX. 


449 


Catadioptric  apparatus  for  light-houses, 

373. 

Catoptric  apparatus  for  light-houses,  372. 
jCauderay's  current-meter,  367. 
Ceiling,  luminous,  employment  of  a,  in 

arc  lighting,  429. 
Changy,  M.  de,  platinum  incandescent 

lamp  of,  117. 
Clamond  incandescent-arc  lamp,  136. 

thermo-electric  battery,  208. 
Clarke  magneto-electric  machine,  232. 
Classification  of  dynamos,  225. 
Clerc,   experiments  of,  with    refractory 

material  in  the  voltaic  arc,  140. 
Coil,  induction,  214. 
Spottiswoode,  217. 
system  of  distribution,  357. 
Coil,  Ruhmkorff,  214. 
Collector,  227. 
Commutation  plane,  228. 

displacement  of,  231. 
Commutator,  227. 

brushes,  Gravier's  plumbago,  297. 
Condenser,  object  of,  in  an  induction-coil, 

215. 
Conductors,  315. 

disposition  of  Edison  street,  329. 
economy  of,  354. 

Edison    junction  -  boxes    for    under- 
ground, 330. 
loss  of  energy  in,  354. 
methods  of  insulation  of,  316. 
relation  between  size  and  cost  of,  and 

current  transmitted.  354. 
Sir  W.  Thomson's  formula  for  design- 
ing, 354. 
underground,  method  of  joining,  used 

by  Jablochkoff  company,  323. 
Cooling,  Dulong  and  Petit's  law  of,  188. 
Newton's  law  of,  188. 
of  a  wire  in  a  vacuum,  188. 
ways  of,  in  a  wire  exposed  to  the  air, 
187. 
Cost  of  arc  light  in  the  factory  of  MM. 

Thomas  and  Powell,  424. 
in  the  fast-freight  department  of  the 
Paris,    Lyons,    and    Mediterranean 
Railway,  421. 
in  the  freight  depot  of  the  Northern 

Railroad  Company,  France,  419. 
produced  by  Alliance  machine,  418. 
produced  by  Bunsen  battery,  418. 


Cost  of  arc  light  produced  by  Gramme 
machine,  419. 

Rouen  tests  of  the,  426. 
Cost  of  Jablochkoif  candle,  427,  432. 

electric  light  in  London,  434. 

lighting  by  incandescent  light,  439. 

lighting  by  sun-lamp,  431. 

lighting     by    Werdermann  -  Reynier 
lamps,  437. 

Siemens  system  of  electric  lighting, 

428. 

Coulomb,  44. 
Crompton  arc  lamp,  81. 
Cruto  incandescent  lamp,  181. 
Current,  direct,  212. 

extra,  215. 

induced,  212. 

induced,  two  ways  of  producing,  214. 

inducing,  212. 

inverse,  212. 

Lane-Fox  regulator  of  intensity  of  the, 
326. 

Maxim  regulator  of  intensity  of,  268. 

practical  unit  of,  44. 

Currents,    Ampere's    discovery    of    the 
mutual  action  of,  211. 

Foucault,  224. 

Foucault,  Faraday's  experiment,  224. 
Cut-out,  automatic,  Brush,  96. 

De  Mersanne,  93. 

Gerard,  92. 

Weston,  97. 

Wood,  97. 

Daniell  battery,  199. 
Davy's  discovery  of  the  voltaic  arc,  21. 
Debrun  candle,  114. 

Deprez's  method  of  compound  winding 
of  dynamos,  340,  341. 

system  of  distribution,  338. 
Dioptric  apparatus  for  light-houses,  373. 
Distribution,  conditions  of  a  general,  324. 

Edison  multiple-series  system  of,  355. 

first  mode  of,  314. 

Gravier's  system  of,  333. 

induction-coil  system  of,  357. 

method  of,  for  lighting  the  port  of 
Havre  with  Jablochkoff  candles,  317. 

secondary,  generator  system  of,  357. 

summary  of  the  conditions  to  be  com- 
plied with,  325. 

system  of  Goulard  and  Gibbs,  358. 


450 


INDEX. 


Distribution,  system  of  Marcel  Deprez, 
338. 

Divisibility  of  the  electric  light,  359. 

Division  of  the  electric  light,  conditions 
under  which  it  must  be  carried  out 
'    to  prevent  loss  of  light,  360. 

Draper's  experiments  on  relation  between 
temperature  and  light,  190. 

Drummond  light,  11. 
as  modified  by  Tessie  du  Motay,  11. 

Duboscq's  arc  lamp,  63. 

Ducretet's  incandescent-arc  lamp,  134. 

Dynamo  -  electric    machine.      (See    Ma- 
chine, dynamo-electric.) 

Dyne,  C.  G.  S.  unit  of  force,  40. 

Edison  canalization,  329. 

dynamo-electric  machine,  273. 

dynamo,  Howell's  measurement  of,  308. 

dynamo,  Munich  committee's  measure- 
ment of,  312. 

first  researches  of,  in  incandescence, 
148. 

junction-boxes  for  underground  con- 
ductors, 330. 

lamp.    (See  Lamp,  Edison.) 

meter,  364. 

method  of  regulating  dynamos,  345. 

multiple-series  system  of  distribution, 
355. 

registering  meter,  365. 

safety-catches,  331. 

street  conductors,  disposition  of,  in  first 

New  York  district,  329. 
Efficiency,  commercial,  of  the  dynamo, 
302. 

conditions  of,  in  the  arc  lamp,  303. 

conditions    of,    in    the     incandescent 
lamp,  187. 

electrical,  of  the  dynamo,  302. 

generative,  of  the  dynamo,  301. 

meaning  of,  298. 

practical  generative,  of  the  dynamo, 
301. 

dynamo,  300. 

electric  system,  353. 

gas-engine,  441. 

heat-engine,  299. 

water-wheel,  299. 
Electrical  induction,  211. 

units,  37,  42. 

units,  summary  of,  45. 


Electricity  and  gas,  difference  between, 
in  the  relation  of  large  and  small 
lights,  361. 

dynamic,  C.  G.  S.  unit  of  potential,  43. 

dynamic,  C.  G.  S.  unit  of  quantity,  43. 

dynamic,  discovery  of,  by  Volta,  20. 

dynamic,  or  current,  29. 
Electricity,  static,  28. 

static,  C.  G.  S.  unit  of  potential,  42. 

static.  C.  G.  S.  unit  of  quantity,  42. 

theory  of,  28. 

static,  experiments  of  Grey,  15. 

experiments  of  Hawksbee,  14. 

experiments  of  Otto  von  Guericke,  11. 

experiments  of  Wall,  13. 

experiments  of  Watson,  18. 
Electric  capacity,  C.  G.  S.  unit  of,  44. 
Electric  light,  different  kinds  of,  32. 

first  use  in  the  theatre,  22. 

how  the,  is  produced,  32. 

limit  of  temperature  in,  361. 

on  vessels,  earliest  use  of,  24. 

so-called  problem  of  divisibility  of  the, 
359. 

the  first,  18. 
Electric  spark,  colors  of,  to  what  due,  18. 

experiments  with  the,  17. 

first  production  of,  from  the  human 

body  by  Du  Fay,  17. 
Electro-magnet,  Arago's  discovery  of  the, 

211. 

Electro  -  magnetic  system  of  measure- 
ment, 43. 

Electrometer,  early,  20. 
Electro-motive  force,  30,  39. 

C.  G.  S.  unit  of,  42,  43. 

practical  unit  of,  44. 
Electro-motor,  Elias,  257. 

Pacinotti,  255. 

Page,  256. 

Electro-static  system  of  measurement,  42. 
Elias  electro-motor,  257. 
Energy,  37. 

kinetic,  37. 

potential,  38. 

Engine,  gas-,  at  the  Paris  Exhibition, 
443. 

comparative  cost  of  the,  and  steam-en- 
gine, 442. 

efficiency  of  the,  441. 
Engine,  heat-,  maximum  theoretical  effi- 
ciency, 299. 


INDEX. 


451 


Engine,  steam-,  how  the  efficiency  is  reck- 
oned, 350. 

Erg,  C.  G.  S.  unit  of  work,  40. 

Exhibition,  Paris,  gas-engine  at  the, 
443. 

Factory-lighting  with  the  arc  light,  424. 
Faraday's  discovery  of  induction,  211. 

experiment  to  show  the  existence  of 

Foucault  currents,  224. 
Farad,  the,  45. 

Farmer,  Wallace-,  dynamo-electric  ma- 
chine, 287. 

Faure  storage-battery,  204. 
Feeders,  Edison,  329. 
Ferranti    alternating  -  current   machine, 

263. 
Field,  galvanic,  213. 

magnetic,  213. 

magnets,  four  ways  of  exciting,  220. 
Foot-pound,  value  of,  in  ergs,  41. 
Force,  C.  G.  S.  unit  of,  40. 

electro-motive,  39. 

electro-motive,  practical  unit  of,  44. 

lines  of  magnetic,  214. 
Foucault  arc  lamp,  61. 

carbons,  46. 

currents,  224. 
Fountain,  luminous,  412. 
Fresnel's  catadioptric  light-house  appa- 
ratus, 373. 

dioptric  light-house  apparatus,  373. 

Gaiffe's  arc  lamp,  70. 
Galvanic  field,  213. 

Gas  and  electricity,  difference  between, 
in  the  relation  of  large  and  small 
lights,  361. 

Gas-engine  at  the  Paris  Exhibition,  443. 
comparative  cost  of  the,  and  the  steam- 
engine,  442. 
efficiency  of  the,  441. 
Gas-flame,  comparative  economy  of,  as  a 
light  -  producer    and    incandescent 
lamp,  193. 

expenditure  of  power  per  candle,  193. 
limit  of  temperature  in  a,  361. 
Gas,  invention  of,  8. 
Geisler  mercury  air-pump,  159. 
Gerard  arc  lamp,  82. 

Gerard  arc  lamp  with  converging  car- 
bons, 108. 


]  Gerard  automatic  cut-out,  92. 
Generator,  secondary-,  system  of  distribu- 
tion, 357. 

Gibbs,  Goulard  and,  system  of  distribu- 
tion, 358. 

Girouard's  arc  lamp,  66. 
Globes,  loss  of  light  with  different,  432. 
Gordon  alternating-current  machine,  264. 
Goulard  and  Gibbs  system  of  distribu- 
tion, 358. 

Gramme  arc  lamp,  74 
armature,  242. 
dynamo,  240. 
dynamo,  measurement    of,   by    Paris 

committee,  306,  307. 
precursors  of,  255. 
Gravier's  regulator,  335. 
rheometric  regulator,  335. 
plumbago  commutator-brushes,  297. 
system  of  distribution.  333. 
Greener  and  Staite  carbon  incandescent 

lamp,  119. 
Grove  battery,  200. 
Gulcher  arc  lamp,  66. 

Harrison  arc  lamp,  59. 

Havre,  port  of,  installation  for  lighting 

the,  317. 

Heat,  C.  G.  S.  unit  of,  42. 
mechanical  equivalent  of,  41. 
units,  41. 

Heat-engine,  efficiency  of,  299. 
Holmes  magneto-electric  machine,  236. 
Hopkinson  current-meter,  366. 
Horse-power,  actual,  in  the  steam-engine, 

300. 
equivalent  of,  in  electrical  measure,  44, 

45. 

indicated,  300. 

value  of  (English  and  French),  40. 
value  of,  in  ergs  (English  and  French), 

41. 
Houston  and   Thomson  storage-battery, 

205. 

Howell's  measurement  of  Edison  dyna- 
mo, 308. 

Incandescence  in  the  air,  36. 

principle  of,  124. 
Incandescence,  history  of,  116. 
Incandescent  lamp.    (See  Lamp,  incan- 
descent.) 


452 


ItfDEX. 


Induced  current,  two  ways  of  producing, 

214. 
Induction-coil,  214. 

Spottiswoode,  217. 

system  of  distribution,  357. 
Induction,  electrical,  211. 

Faraday's  discovery  of,  211. 

in  polar  armatures,  230. 

in  ring  armature,  228. 
Intensity  of  current,  31. 

Jablochkoff  candle.  98. 
construction  of,  101. 
cost  of  the,  427,  432. 
office  of  the  insulating  material  in, 

138. 
Jablochkoff  kaolin  incandescent    lamp, 

216. 

pyro-electric  battery,  210. 
Jacobi's  law  of  maximum  result,  and  its 

wrong  interpretation,  301. 
Jamin  candle,  112. 
Jaspar's  arc  lamp,  70. 
Joel  incandescent-arc  lamp,  130. 
Joule,  the,  45. 
Junction-boxes  for  Edison  underground 

conductors,  330. 

Junction-box  for  underground  conduct- 
ors used  by  Jablochkoff  Company, 
323. 

Jurgensen  dynamo-electric  machine,  279. 
dynamo,    measurement    of,  by    Paris 
committee,  306. 

Kabath  storage-battery,  206. 
Kilogramme,  value  of,  in  ergs,  40. 
Konn  incandescent  lamp,  121. 
Kosloff  incandescent  lamp,  121. 

Ladd  dynamo-electric  machine,  238. 
Lamp,  arc,  Archereau's,  67. 

Brush,  82. 

Burgin,  65. 

carbons  for,  46. 

Carre,  71. 

Crompton,  81. 

De  Mersannes,  74 

differential,  78. 

Duboscq,  63. 

Foucault,  61. 

Gaiffe,  70. 

Gerard,  82. 


Lamp,  arc,  Gerard,  with  converging  car- 
bons, 107. 

Girouard,  66. 

Gramme,  74. 

Gulcher,  66. 

hand-regulated,  57. 

Harrison,  59. 

Jaspar,  70. 

Pilsen,  82. 

problem  of  placing  a  number  on  one 
circuit.     How  solved,  71. 

Rapieff,  with  converging  carbons,  105. 

safety,  of  Reynier,  132. 

Serrin,  63. 

Serrin,  modified  so  as  to  burn  several 
on  one  circuit,  73. 

shunt-circuit,  72. 

Siemens,  79. 

single-light,  55. 

used  in  French  light-houses,  378. 

Wallace,  77. 

Weston,  86. 

without  mechanism,  105. 

Wood,  88. 

Wright,  59. 

comparative   economy  of,  and  incan- 
descent lamp,  193. 

conditions  of  economy  in  the,  303. 

elements  which  determine  the  light  of, 
303. 

limit  to  the  light  obtainable  with  the, 
303. 

measurements  of,  304. 

photometric  measurement  of  305. 
Lamp,  Argand,  improvement  of  Quin- 
quet,  6. 

Argand,  invention  of,  5. 

Carcel,  7. 

Carcel,  illuminating  power  of,  7. 

comparative  economy  of  arc,  candle, 
and  incandescent,  331. 

early  form  of,  1. 
Lamp,  incandescent-arc,  Sawyer,  136. 

Clamond,  136. 

cost  of  lighting  by  the  Werdermann- 
Reynier-Napoli,  437. 

Ducretet,  134. 

Joel,  130. 

latest  form  of  the  Reynier,  131. 

Reynier,  123. 

principle  of,  36. 

Werdermann,  125. 


INDEX. 


453 


Lamp,  incandescent,  Bernstein,  181. 

carbon,  advantage  of  a  natural  fiber, 
157. 

comparative  economy  of,  and  arc  lamp, 
193. 

conditions  of  efficiency  in  the,  187. 

conditions  of  success  in,  151. 

cost  of  lighting  by  the,  439. 

Cruto,  181. 

De  Changy,  117. 

DeMoleyns,  117. 

direction  in  which  to  improve  the,  193. 
Lamp,  incandescent,  Edison,  148. 

bamboo  carbon,  158. 

examples  of  various  forms  of  fixtures, 
163-166. 

first  forms  of  the  carbon,  155. 

mining,  170. 

platinum,  152. 

platinum,  why  abandoned,  155. 

platinum,  with  regulator,  153,  154.       . 

present  form  of,  162. 

with  rheostat  for   varying  the  light, 

164. 

Lamp,  incandescent,  expenditure  of  pow- 
er per  candle,  113. 

Greener  and  Staite,  119. 

Jablochkoff  kaolin,  216. 

Konn,  121. 

Kosloff,  121. 
Lamp,  incandescent,  Lane-Fox,  177. 

method  of  sealing,  178. 
Lamp,  incandescent,  Lodyguine,  119. 
Lamp,  incandescent,  Maxim,  179. 

mode  of  attaching  filament  to  leading 
wires,  180. 

treatment  of  the  filament  to  make  it 

compact,  179. 

Lamp,  incandescent,   mode    of    sealing 
filament  into  the  globe,  165. 

platinum,  116. 

Starr,  118. 

superior  economy  of,  as  compared  with 

a  gas-flame,  192. 
Lamp,  incandescent,  Swan,  170. 

mining,  176. 

preparation  of  the  filament,  172. 

treatment  of  the  filament  so  as  to  free 

it  of  occluded  air,  171. 
Lamp,  oil,  for  light-houses,  373. 

platinum  gauze,  10. 

Roman,  2. 


Lamp,  sun-,  137. 
advantage  of,  142. 
cost  of  lighting  with  the,  431. 
Lamps,  incandescent,  measurement   of, 

182. 

by  the  Paris  committee,  185. 
by  the  Munich  committee,  186. 
Lamps,  multiple-arc  arrangement  on  cir- 
cuit, 222. 

series  arrangement  of,  on  circuit,  222. 
Lane-Fox  incandescent  lamp,  177. 
regulator  of  the  intensity  of  the  cur- 
rent, 326. 
Law,  Ohm's,  39. 
Length,  unit  of,  40. 
Leroux,  experiments  of,  with  refractory 

material  in  the  voltaic  arc,  138. 
Leyden-ja"r,  invention  of  the,  19. 
Light,    comparative     economy     of    arc 
lamps,    candles,    and    incandescent 
lamps,  331. 
Light,  electric-,  arrangement  of,  on  the 

steamer  Amerique,  401. 
at  sea,  399. 
comparative  intensity  of,  and  sunlight, 

384. 
comparative   range   of,  and  oil-light, 

383. 

complete  field  apparatus  for  the,  396. 
cost  of  the  arc,  by  Alliance  machine, 

418. 

by  Bunsen  battery,  418. 
by  Gramme  machine,  419. 
by  Siemens  system,  428. 
cost  of  the  arc  in  fast-freight  depart- 
ment of  the  Paris,  Lyons,  and  Medi- 
terranean Railway,  421. 
cost  of  the  arc  in  freight  depot  of  the 
Northern  Railroad  Company,  France. 
419. 

cost  of,  in  London,  434. 
early  use  of,  in  military  operations, 

388. 
employment  of  the  luminous  ceiling  in 

lighting  by  the,  429. 
factory  lighting  by  the,  424. 
first  appearance  of  the,  in  the  theatre, 

407. 

first  use  of,  on  steam-vessels,  389. 
increase  in  intensity  of  the,  by  means 

of  light-house  apparatus,  383. 
in  the  French  navy,  393,  403. 


454 


INDEX. 


Light,  electric-,  lamp  for  illuminating  an 
actor  in  a  play  with  the,  411. 

lighting  of  out-door  works  of  construc- 
tion with  the  arc,  434. 

lighting  of  theatres  by,  415. 

limit  of  temperature  in  the,  361. 

method  of  using,  to  light  a  distant  ob- 
ject, 406. 

on  ships,  399. 

production  of  a  rainbow  by  the,  in  the 
theatre,  409. 

production  of  specters  by  the,  in  the 
theatre,  414. 

projector  of  Mangin  for  the,  394. 

projector  of  Mangin  for  the,  range  of, 
398. 

protection  afforded  to  war-vessels  by, 
405. 

representation  of  lightning  by  the,  in 
the  theatre,  410. 

representation  of  the  sun  by  the,  in  the 
theatre,  408. 

Rouen  tests  of  cost  of  the,  426. 

so-called  problem  of  divisibility  of  the, 
359. 

use  of,  in  the  siege  of  Paris,  392. 

use  of  the,  in  optical  telegraphy,  406. 

use  of,  to  produce  the  luminous  fount- 
ain, 412. 

Light,  elements  which  determine  the,  of 
the  arc  lamp,  303. 

geographic  range  of  a,  375. 
Lighter,  Reynier  automatic,  132. 
Light-house,  Planier,  381. 

with  luminous  plume,  384. 
Light-houses,  catadioptric  apparatus  for, 
373. 

catoptric  apparatus  for,  372. 

different  orders  of,  376. 

dioptric  apparatus  for,  373. 

early,  371. 

oil-lamp  for,  373. 

Lighting,  cost  of,  by  the  incandescent 
lamp,  439. 

electric,  in  France,  435. 

of  the  residence  of  Sir  W.  G.  Arm- 
strong, 445. 

of  the  residence  of  Mr.  Spottiswoode, 
445. 

use  of  accumulators  in,  444. 
Light,  loss  of,  with  different  globes,  432. 

luminous  range  of  a,  375. 


Light,  method  of  measuring  the  inten- 
sity of  a,  183. 

Lightning,  representation  of,  in  the  thea- 
tre by  the  electric  lignt,  410. 
Light,  range  of  a ;  difference  between  geo- 
graphic and  luminous,  375. 
relation  between,  and  heat  expenditure, 

191. 

relation  between,  and  temperature,  190. 
Lights,  scintillating,  in  light-houses,  378. 

varieties  of,  in  light-houses,  377. 
Lime-light,  11. 
Lodyguine    incandescent    carbon   lamp, 

119. 
Lontin  dynamo-electric  machine,  287. 

Machine,  disposition  of  parts  of,  223. 
Machine,  dynamo-electric,  action  of,  222. 

Brush,  279. 

Brush,  measurement  of,  by  Paris  com- 
mittee, 307. 

Biirgin,  289. 

Biirgin,  measurement  of,  by  Paris  com- 
mittee, 307. 

Machine,  dynamo-electric,  definition  of, 
218. 

Deprez's  method  of  compound  winding 

of,  340,  341. 
Machine,  dynamo-electric,  Edison,  273. 

armature  of,  275. 

compound  winding  of  the,  345. 

Hovvell's  measurement  of,  308. 

Munich  committee's  measurement  of, 
312. 

steam,  275. 

Machine,  dynamo-electric,  efficiency  of, 
298. 

Ferranti,  alternating-current,  263. 

Ferranti,  alternating-current,  armature 

of,  263. 
Machine,  dynamo-electric,  Gramme,  240. 

armature  of  alternating-current,  249. 

armature  of  continuous-current,  242. 

alternating-current,  248. 

alternating-current,  self-exciting,  250. 

commutator  of,  243. 

double  ring,  248. 

first  form  of,  242. 

Fontaine's  experiments  on  the  effect  of 
speed  and  distance  of  machine  from 
lamps,  245. 

for  a  number  of  lamps,  245. 


INDEX. 


455 


Machine,  dynamo  -  electric,  Gramme, 
measurement  of,  by  Paris  commit- 
tee, 306,  307. 

octagonal,  248. 

Machine,  dynamo-electric,  Gordon  alter- 
nating-current, 264. 

Jurgensen,  279. 

Jurgensen,  measurement  of,  by  Paris 
committee,  306. 

Ladd,  238. 

Lontin,  287. 

Lontin  alternating-current,  288. 

Maxim,  267. 

Maxim,  measurement  of,  by  Paris  com- 
mittee, 307. 

Niaudet,  287. 

Pacinotti,  253. 

principle  of  mutual  accumulation.  239. 
Machine,  dynamo-electric,  regulation  of, 
Brush,  for  arc  lighting,  354. 

Deprez,  340,  341. 

Edison,  345. 

Edison  automatic,  348. 

Edison,  for  central  stations,  347. 

Perry,  344. 

Weston,  for  arc  lighting,  352. 

Weston,  for  incandescent  lighting,  350. 
Machine,  dynamo-electric,  separately  ex- 
cited, 220. 

series-wound,  221. 

shunt-wound,  221. 
Machine,  dynamo-electric,  Siemens,  257. 

armature  of,  alternating-current,  261. 

armature  of,  continuous-current,  257. 

alternating-current,  261. 

measurement  of,  by  Paris  committee, 

307. 

Machine,  dynamo-electric,  Wallace-Far- 
mer, 287. 

Weston,  266. 

Weston,  measurement  of,  by  Paris  com- 
mittee, 307. 

Wilde,  237. 

Wood,  253. 

Worms  de  Romilly,  256. 
Machine,  magneto-electric,  Alliance,  233. 

Clarke,  232. 

definition  of,  218. 

De  Meritens,  alternating-current,  291. 

De  Meritens,  continuous-current,  295. 

first,  232. 

Gramme,  laboratory,  241. 


Machine,  magneto-electric,  Holmes,  236. 

Nollet,  233. 

Pixii,  232. 

Saxton,  232. 

Van  Malderen,  236. 
Machines,  classification  of,  225. 

conditions  upon  which  efficient  work- 
ing depends,  297. 

measurement  of,  304. 

reason  for  the    displacement  of    the 
brushes  of,  231. 

theoretical  principles  of,  217. 

Thompson's  classification  of,  225. 
Magnet,  electro-,  Arago's  discovery  of, 

211. 
Magnetic  field,  213. 

force,  lines  of,  214. 

Magneto  -  electric    machines.    (See    Ma- 
chines, magneto-electric.) 
Magnets,  field,  different  ways  of  exciting 
the,  220. 

Alliance  machine,  234. 

Brush,  279. 

De  Meritens  alternating-current   ma- 
chine, 291. 

De  Meritens  continuous-current   ma- 
chine, 295. 

Edison  dynamo,  275. 

Edison  steam-dynamo,  277. 

Ferranti  machine,  263. 

Gramme  alternating-current  machine, 
249. 

Gramme  continuous-current  machine, 
240. 

Gramme  octagonal  machine,  248. 

Gordon   alternating-current  machine, 
264. 

Lontin  machine,  288. 

Maxim  dynamo,  267. 

Pacinotti  machine,  255. 

Siemens  alternating-current  machine, 
261. 

Siemens  continuous-current   machine, 
257. 

Wilde  machine,  238. 

Weston  dynamo,  266. 

principle  of  self-excitation  of,  239. 
Mangin  electric-light  projector,  394. 

range  of,  398. 
Mass,  unit  of,  40. 
Maxim  current-regulator,  268. 

dynamo-electric  machine,  267. 


456 


INDEX. 


Maxim  dynamo,  measurement  of,  by  Paris 

committee,  307. 
incandescent  lamp,  179. 
Mechanical  equivalent  of  heat,  41. 
Mechanical  units,  40. 
Measurement,  electro-magnetic  system  of, 

43. 

electro-static  system  of,  42. 
of  Edison  dynamo  by  Ho  well,  308. 
of  incandescent  lamps,  182. 
Measurements  of  dynamos  and  arc  lamps, 

304. 

of  storage-batteries,  206. 
Meritens,  de,  dynamo-electric    machine, 

291. 

Meritens  storage-battery,  205. 
Mersanne  arc  lamp,  94. 
Mersanne  automatic  cut-out,  93. 
Meter,  Ayrton  and  Perry's  work,  3G9. 
Boys  current,  366. 
Boys  work,  368. 
Cauderay's  current,  367. 
Edison,  364. 
Edison  registering,  365. 
Hopkinson's  current,  366. 
Meters,  current,  363. 

electric,  two  classes  of,  363. 
Military  operations,  use  of  the  electric 

light  in,  388. 
Mirror,   magic,   for   the   production    of 

lightning  in  the  theatre,  411. 
Moleyns,  Frederick  de,  platinum  incan- 
descent lamp  of,  117. 
Motor,  electro-,  Elias,  257. 
Pacinotti,  255. 
Page,  256. 
Multiple-arc  arrangement  of  lamps  on  a 

circuit,  222,  324. 

Munich  committee's  measurement  of  Edi- 
son dynamo,  312. 

Munich  committee's  measurement  of  in- 
candescent lamps,  186. 

Navy,  electric  light  in  the  French,  393, 
403. 

Needle,  Oerstedt's  observation  of  the  de- 
flection of  a  magnetic,  by  a  current 
or  magnet,  211. 

Niaudet  dynamo-electric  machine,  287. 

Oerstedt's  observation  of  the  effect  of  a 
current  on  a  magnetic  needle,  211. 


Ohm's  law,  32,  39. 
Ohm,  the,  44. 

Pacinotti  dynamo-electric  machine,  255. 

electro-motor,  255. 
Page  electro-motor,  256. 
Paris  committee's  measurements  of  dy- 
namos and  arc  lamps,  305. 
Paris  committee's  measurement  of  incan- 
descent lamps,  185. 

Paris  exhibition,  gas-engine  at  the,  443. 
Paris,  use  of  the  electric  light  in  the  siege 

of,  392. 

Perry,  Ayrton  and,  work-meter,  369. 
Perry's  regulation  of  dynamos,  344. 
Photometer,  Bunsen,  184. 
Pixii  magneto-electric  machine,  232. 
Pilsen  arc  lamp,  82. 
Pile,  voltaic,  invention  of,  20. 
Plante  storage-battery,  203. 
Platinum,  effect  of  withdrawing  the  air 

from  its  pores,  154. 
Platinum  gauze  gas-lamp,  10. 
Platinum  incandescent  lamp,  116. 
Polarization,  199. 
Potential,  30,  39. 

C.  G.  S.  unit  of  difference  of,  42,  43. 

measurement  of,  183. 

practical  unit  of,  44. 
Pound,  foot-,  value  of,  in  ergs,  41. 
Power,  definition  of,  38. 

practical  unit  of,  44. 
Power,  horse-,  equivalent  of,  in  electrical 
measure,  44,  45. 

indicated,  300. 

value  of,  English,  French,  40. 

value    of,  in    ergs,   English,   French, 

41. 

Projector,  Mangin,  for  the  electric  light, 
394. 

range  of,  398. 
Pump,  mercury  air-,  Geisler,  159. 

Sprengel,  161. 

Quantity,  practical  unit  of,  44. 

Rainbow  produced  by  the  electric  light 

in  the  theatre,  409. 
Range,  geographic,  of  a  light,  375. 
luminous,  of  a  light,  375. 
of  a    light,   difference    between    geo- 
graphic and  luminous,  375. 


INDEX. 


457 


Rapieff  arc  lamp  with   converging  car- 
bons, 105. 

Reflectors,  plate,  of  M.  Boulard,  429. 
Regulation  of  dynamos,  Brush,  for  arc 
lighting,  354. 

Deprez,  340,  341. 

Edison,  345. 

Edison's  automatic,  348. 

Edison  station,  347. 

Perry,  344. 

Weston  method  for  arc  lighting,  352. 

Weston  method  for  incandescent  light- 
ing, 350. 
Regulator,  Lane-Fox  current,  326. 

Maxim  current,  268. 

Gravier's,  335. 

Gravier's  rheometric,  335. 
Resistance,  31. 

C.  G.  S.  unit  of,  42,  43. 

method  of  measuring,  182. 

practical  unit  of,  44. 

proper  relation  between  that  of  the  gen- 
erator and  external  circuit,  301. 
Reynier  automatic  lighter,  132. 

battery,  201. 

incandescent-arc  lamp,  123. 

incandescent-arc  lamp,  latest  form,  131. 

safety  arc  lamp,  132. 
Romilly,   Worms   de,    dynamo  -  electric 

machine  of,  256. 
Ruhmkorfl  coil,  214. 

Safety  apparatus,  automatic,  90. 
Safety-catches,  Edison,  331. 
Sawyer  incandescent-arc  lamp,  136. 
Saxton  magneto-electric  machine,  232. 
Secondary  battery,  202. 

generator  system  of  distribution,  357. 
Sellon-Volckmar  storage-battery,  205. 
Series  arrangement  of  lamps  on  a  circuit, 

222,  324. 

Serrin's  arc  lamp,  63. 
Ships,  electric  light  on,  399. 
Siemens  arc  lamp,  79. 

armature,  236. 

dynamo-electric  machine,  257. 

dynamo,    measurement    of,  by    Paris 
committee,  307. 

system  of  electric  lighting,  cost  of  the, 

428. 
Spottiswoode,  induction-coil  of,  217. 

lighting  of  residence  of,  445. 


Specters,    production    of,  in   the    thea- 
tre by  means  of  the  electric  light, 
414. 

Spherique,  Moyenne,  intensity  of  light  of 
arc  lamp,  305. 

Sprengel  mercury  air-pump,  161. 

Staite,  Greener  and,  carbon  incandescent 
lamp,  119. 

Star-candle,  origin  of  the  name,  5. 

Starr,  experiments  of,  with  carbon  incan- 
descent lamp,  118. 
incandescent  lamp,  118. 

Steam-engine,  comparative  cost  of  the, 
and  the  gas-engine,  442. 

Steam  dynamo,  Edison,  275. 

Storage-battery,  202. 

Street-lighting  by  means  of  candles,  4. 

Sun,  electric-light  apparatus  to  represent 
the,  in  the  theatre,  408. 

Sun-lamp,  137. 
advantage  of,  142. 
cost  of  lighting  with  the,  431. 

Sunlight,  comparative  intensity  of,  and 
the  arc  electric  light,  384. 

Sutton  storage-battery,  206. 

Swan  incandescent  lamp,  170. 

Telegraphy,  optical,  use  of  the  electric 

light  in,  406. 

Temperature,  absolute  zero  of,  299. 
importance  of  high,   in  incandescent 

lamps,  191. 

limit  of,  in  electric  light,  361. 
limit  of,  in  gas-flame,  361. 
limit  of,  in  incandescent  lamp,  192. 
relation  between  the,  of  a  body  and  the 

light  yielded  by  it,  190. 
Tension,  30. 
Theatre.    Electric  lamp  for  illuminating 

an  actor  in  a  play,  411. 
electric  lamp  for  lighting  a  particular 

part  in  a  scene,  412. 
first  appearance  of  the  electric  light  in 

the,  407. 
lighting  of  the,  by  the  electric  light, 

415. 
production  of  a  rainbow  in  the,   by 

means  of  the  electric  light,  409. 
production  of  specters  in  the,  by  the 

electric  light,  414. 
representation  of  lightning  in  the,  by 

the  electric  light,  410. 


458 


INDEX. 


Theatre,  representation  of  the  sun  in  the, 

by  means  of  the  electric  light,  408. 
use  of  electric  light  to  produce  the  lu- 
minous fountain  in  the,  412. 

Thompson's  classification  of  dynamo-ma- 
chines, 225.- 

Thomson  and  Houston  storage-battery, 
205. 

Time,  unit  of,  40. 

Tomasi  battery,  201. 

Unit  of  heat,  C.  G.  S.  system,  42. 

length,  40. 

mass,  40. 

time,  40. 

work,  40. 
Units,  C.  G.  S.  system  of,  40. 

electrical,  37,  42. 

electrical,  summary  of,  45. 

heat,  41. 

mechanical,  40. 

practical,  44. 

Van  Malderen  magneto-electric  machine, 

236. 

Volta,  battery  of,  20. 
Voltaic  arc.    (See  Arc,  voltaic.) 
battery,  invention  of  the,  20. 
Volt,  the,  44. 

Wallace  arc  lamp,  77. 
Wallace  -  Farmer  dynamo  -  electric  ma- 
chine, 287. 


War,  use  of  the  electric  light  in,  388. 
Watt,  the,  45. 

Werdermann  incandescent-arc  lamp,  125. 
Werdermann  -  Reynier  incandescent-arc 

lamp,  cost  of  lighting  by,  437. 
Weston  arc  lamp,  86. 
automatic  cut-out,  97. 
dynamo-electric  machine,  266. 
method  of  regulating  dynamos  for  arc 

lighting,  352. 

method  of  regulating  dynamos  for  in- 
candescent lighting,  350. 
dynamo,  measurement  of,  by  Paris  com- 

'  mittee,  307. 
Wheatstone  bridge,  182. 
Wilde  candle,  110. 

dynamo-electric  machine,  237. 
Wood  arc  lamp,  88. 
automatic  cut-out,  97. 
dynamo-electric  machine,  253. 
Work,    available,    in    external    circuit, 

302. 

C.  G.  S.  unit  of,  40. 
definition  of,  37. 
practical  unit  of,  44. 
relation  of  external  and  internal,  in  the 

series  dynamo,  302. 
relation  of  external  and  internal,  in 

shunt-dynamo,  302. 
unit  of,  40. 
Wright  arc  lamp,  59. 

Zero,  absolute,  of  temperature,  299. 


THE    END. 


Important  Works  on 

ELECTRICITY 


A  PHYSICAL  TREATISE  ON   ELECTRI- 
CITY AND   MAGNETISM. 

By  J.  E.  H.  GORDON,  B.  A., .  Assistant  Secretary  of  the  British 
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THE  MODERN  APPLICATIONS  OF  ELEC- 
TRICITY. 

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IMPORTANT  WORKS  ON  ELECTRICITY.— (Continued.) 

ELECTRICITY    AND    MAGNETISM. 

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THE  ART  OF  ELECTRO-METALLURGY, 
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etc.,  and  to  all  persons  who  wish  to  obtain  in  a  compact  form  an  explanation  of 
the  principles  and  facts  upon  which  the  art  is  based,  the  circumstances  under 
which  nearly  every  known  metal  is  deposited,  and  the  special  details  of  technical 
workshop  manipulation  in  the  galvano -plastic  art.  I  have  also  given  an  histcrical 
sketch  of  the  development  of  the  subject,  arranged  in  chronological  order.  I 
have  endeavored  not  only  to  make  the  book  a  treatise  on  the  practical  art  of 
electro-metallurgy,  but  also  to  include  an  outline  of  the  science  of  electro- 
chemistry, upon  which  that  art  is  based  ;  and  I  have  spared  no  trouble  to  make 
the  book  as  perfect  as  I  could.  The  most  complete  portions  are  those  which 
treat  of  the  common  methods  of  silvering,  gilding,  molding ;  the  deposition  of 
copper,  nickel,  brass,  iron,  and  tin ;  the  special  details  of  the  art ;  and  the  ac- 
counts of  such  experiments  and  processes  with  the  less  common  metals  as  sci- 
entific investigators  and  practical  inventors  may  be  likely  to  further  examine,  or 
practically  apply.  Numerous  experiments  of  my  own  on  the  subject  (many  of 
them  through  want  of  previous  opportunity  being  now  for  the  first  time  pub- 
lished) are  scattered  through  the  first  part  of  the  practical  section  of  the  book; 
a  few  of  them  being  made  to  fill  up  missing  links,  while  the  book  was  in  prog- 
ress."— From  the  Introduction. 


IMPORTANT  WORKS  ON  ELECTRICITY.— (Continued.) 

LIGHT  AND  ELECTRICITY: 

NOTES  OF  TWO  COURSES  OF  LECTURES  BEFORE  THE  ROYAL  INSTITU- 
TION OF  GREAT  BRITAIN. 

By  Professor  JOHN  TYNDALL.     i2mo.     Cloth,  $1.25. 

"  In  thus  clearly  and  sharply  stating  the  fundamental  principles  of  electrical 
and  optical  science,  Professor  Tyndall  has  earned  the  cordial  thanks  of  all  inter- 
ested in  education." — From  the  American  Editor's  Preface. 


LESSONS    IN    ELECTRICITY,    AT    THE 
ROYAL  INSTITUTION,   1875-76. 

By  Professor  JOHN  TYNDALL.     i2mo.     Cloth,  $1.00. 


ELEMENTARY   TREATISE    ON    NATU- 
RAL   PHILOSOPHY. 

By  A.  PRIVAT  DESCHANEL,  formerly  Professor  of  Physics  in  the 
Lyce'e  Louis-le-Grand,  Inspector  of  the  Academy  of  Paris. 
Translated  and  edited,  with  Extensive  Modifications,  by  J.  D.  EVERETT, 

Professor  of  Natural  Philosophy  in  the  Queen's  College,  Belfast. 
Sixth  edition,  revised,  complete  in  Four  Parts.     8vo.     Illustrated  by 

783  Engravings  on  Wood,  and  Three  Colored  Plates. 
Part  I.    MECHANICS,    HYDROSTATICS,   AND    PNEUMATICS. 

Cloth,  $1.50. 

Part  II.  HEAT.     Cloth,  $1.50. 

Part  III.  ELECTRICITY  AND  MAGNETISM.     Cloth,  $1.50. 
Part  IV.  SOUND  AND  LIGHT.     Cloth,  $1.50. 

Complete  in  one  volume,  8vo,  with  Problems  and  Index.     Cloth, 
15-70. 

"  Systematically  arranged,  clearly  written,  and  admirably  illustrated,  showing 
no  less  than  783  engravings  on  wood  and  three  colored  plates,  it  forms  a  model 
work  for  a  class  of  experimental  physics.  Far  from  losing  in  its  English  dress 
any  of  the  qualities  of  matter  or  style  which  distinguished  it  in  its  original  form,  it 
may  be  said  to  have  gained  in  the  able  hands  of  Professor  Everett,  both  by  way  of 
arrangement  and  of  incorporation  of  fresh  matter,  without  parting  in  the  transla- 
tion with  any  of  the  freshness  or  force  of  the  author's  text.  "—Saturday  Review. 


These  books  are  sold  by  all  booksellers ;   or  will  be  sent  by  mail,  post-paid,  on 
receipt  of  price,  by 

D.  APPLETON  &  CO.,  Publishers, 

i,  3,  &  5  BOND  STREET,  NEW  YORK. 


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